BRIGHTNESS and COLOUR

Post 712 -by Gautam Shah

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1 Col-18 A ray of Light 32215719528_70dbfd2d22

Brightness and Colour have mutual dependence. Greater brightness leads to sharper visual perception and the colour (spectrum) affects the perceived level of brightness. Physiological and environmental conditions alter the perception of brightness as well as colours. Noon time daylight conditions are accepted as the optimal brightness condition for experiencing the colour. But this condition of high brightness can reduce the contrast between two near by objects and so confuse the colour perception.

3 Col-16 White architecture-2564221

Brightness and colour, both are strongly affected by the immediate past experience. Sudden transition from darkness to brightness or one colour to another affects the pupil dilation.

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Brightness and colour relate to reflection from a surface. The quality of a surface, the texture and its grain orientation vis a vis the directions of illumination and observation, affect the perception. Most of the objects reveal their multiple surfaces concurrently but brightness and colour on each of the face seems different. In this scenario the source of illumination (if solar) and observers both vary their position. As a result colour perception is very dynamic phenomenon. In Architecture or Interior design colour matching or determination of brightness is always worrisome affair.

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Next factor is the context in which objects or scenes are observed. The juxtaposition with a lighter background enhances and darker backdrop setting dulls the perception of brightness and colour.

5 Col-12 Brightness architecture-street-spain-day

Colour perception operates at three basic levels, as the capacity of a surface to reflect light, as emission of light from a hot body and the personal capacity to differentiate various colourations. But the conveyance of the ‘colour related experiences’ is even more difficult. The interpretation of colours varies in different setting of locations, cultures and circumstances. Environment and Terrain are two major factors that alter the colour. Environmental conditions like solar brightness, inclination, orientation, cloud-cast conditions, atmospheric refractions, etc. vary depending on the geographic location. These are further attuned by the surface extent, texture, angle and duration of exposure. The terrain offers very pervasive colour context against which everything is observed. The different terrain effects are really not perceived on the site, but experienced through time-space segmented documents like photographs, paintings, videos or movies.

11 Col-8 Contrasting context Dark brown to Black Edouard Manet Olympia Google Art Project Image 3

Charles Sheeler Whiteness Brightness White Sentinels

ART by Edward Hopper Daylight and Artificial light depiction

6 Col-13 Evening Colours san-nicola-arcella-praia-a-mare-sunset-noon

The conditions at ground level such as surface colour, wetness, snow, vegetation cover, topography, orientation, man-made and natural features, surroundings, density, reflection (albedo), absorption, altitudes etc. determine the colour quality of light. Since all these surface conditions are very localized, the colour variations are conditioned by them. The buildings in surrounding areas, immediate terrain and water bodies have a bearing on the quality of illumination entering a building.

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12 Cantebury Cathedral Day-Night

Illumination in a space is Natural (daylight, chiefly solar origin), Artificial and often combination of both. Daylight has Four important facets, the illuminance, warmth, colour and the variability. Daylight on an outdoor location is a combination of direct sunlight, diffuse sky radiation, and both of these as reflected from the earth and other objects. The brightness and colour of daylight are governed by the sky conditions, like clouds, fog, smoke, atmospheric pollution, morning and evening twilight zones (when the atmospheric scattering of predawn sunlight takes place).

16 Col-5 Twilight colours in sky

The solar radiation as received on the surface of Earth varies from place to place, season to season, day to day and even hour to hour. Equatorial regions receive more radiation, than polar regions. Darker surfaces, like the tropical forests reflect very little radiation, 10 %, compared to snow bound high latitude areas, which nearly reflect 80 % of the energy received. Cloudy and dust polluted areas receive less solar energy. Direct sunlight at noon can have illuminance as high as 120,000 lux (Compared to this moon light is <1 lux). Sunlight is a warm colour light, at noon, the colour-temperatures are about 5500°k, bluish-white or ‘cool colours’ and at sunset, these are about 2700-3000°k (degrees kelvin), are yellowish-white through red or called ‘warm colours’.

8 Col 1 Street-in-Eguisheim France

The reflected light from the exterior surfaces of buildings, roads and pavements affect the illumination on lower floors of the buildings. These cause minor variations due to movements of people, vehicles, ripples on water bodies and leaves of trees. Upper floors of tall buildings, except in similar localities, receive fairly consistent, but very strong daylight from nominal windows. Such floors with low or no sill windows (glass curtain walls) get varying levels of illumination, often strongly coloured.

14 Col-9 2016_Newport_Beach_Boat_Parade_by_D_Ramey_Logan

Reflectance of rooms’ interior surfaces impacts the perception of brightness and colours in a space. The surface reflectance is a function of colour, its texture (matt, dull-sheen, glossy) and the orientation of grains of textures. Extreme levels of brightness, if, are present within the same field of view, can be calibrated by the surface texture and colour. Historic buildings, sites and remains, are conserved with surroundings updated through paved stones of same colour-texture as the original built-form or green lawns. These choices, alter the degree of interior brightness, as well the quality of colour.

Terrain Colours

Similarly cities conserved with enforced thematic colours (blue -Jodhpur, Pink -Jaipur, both in India, white -Santorini, sienna browns -Italian, Piazza del Campo and ), create monotonous colour tonality in interior spaces.

Bowling_Green_Bridge,_Raglan_Castle_-_geograph.org.uk_-_1531252

For artificial illumination sources Brightness and Colour have some sensorial connection. Artificial light sources one commonly accepted rating, the Colour rendering index (CRI). It is supposed to index ‘how the colour will look’. High CRI (nearly equal to daylight in afternoon) will mean colour will look ‘real and right’ and low CRI will mean unreal (weird) and wrong. CRI has limited relevance, if only the illumination source is white (Candles and incandescent bulbs can have high CRI ,but are off-white. The sodium lamps have low CRI but high brightness.

9 Col All Colours

13 Col Brightness_and_colorfulnes

 

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LIST of BLOGS on COLOURS

COLOURS, COATINGS, PAINTS, PIGMENTS

Post 578 by Gautam Shah

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640px-candy_colours_28209906271829

Colours > Wikipedia image > source Candy by Author terren in Virginia

1 UNDERSTANDING LACQUERS

https://interiordesignassist.wordpress.com/2015/08/16/understanding-lacquers/

2 LACQUERS or NC LACQUERS

https://interiordesignassist.wordpress.com/2014/04/27/lacquers-or-nc-lacquers/

3 SOLVENTS for THINNERS

https://interiordesignassist.wordpress.com/2015/08/09/solvents-for-thinners/

4 WOOD SURFACE FINISHING

https://interiordesignassist.wordpress.com/2015/07/13/wood-surface-finishing/

5 PAINT THINNERS Part 2

https://interiordesignassist.wordpress.com/2015/05/14/paint-thinners-part-2/

6 PAINT THINNERS Part 1

https://interiordesignassist.wordpress.com/2015/05/08/paint-thinners-1/

7 ROSEWOOD

https://interiordesignassist.wordpress.com/2015/03/26/rosewood/

8 INDUSTRIAL PAINT FINISHES

https://interiordesignassist.wordpress.com/2015/03/07/industrial-paint-finishes/

9 APPLICATION of COATINGS

https://interiordesignassist.wordpress.com/2015/01/09/application-of-coatings/

10 COATINGS -Surface finishing technologies

https://interiordesignassist.wordpress.com/2014/11/08/coatings-surface-finishing-technologies/

11 CLEAR COATINGS

https://interiordesignassist.wordpress.com/2014/09/12/clear-coatings/

12 FILM FORMING PROCESS in COATINGS

https://interiordesignassist.wordpress.com/2014/09/03/film-forming-process-in-coatings/

13 WOOD SURFACE PREPARATIONS for CLEAR COATINGS

https://interiordesignassist.wordpress.com/2014/04/28/wood-surface-preparations-for-clear-coatings/

14 SHELLAC COATINGS and FRENCH POLISHES

https://interiordesignassist.wordpress.com/2014/04/26/shellac-coatings-and-french-polishes/

15 VARNISH

https://interiordesignassist.wordpress.com/2014/04/25/varnish/

16 MULTI COATS of PAINT SYSTEMS

http://talking-interior-design.blogspot.in/2014/03/multi-coats-of-paint-systems.html

17 WOOD FINISHES

http://talking-interior-design.blogspot.in/2014/07/wood-finishes.html

18 CLEAR COATINGS

http://talking-interior-design.blogspot.in/2015/03/clear-coatings.html

19 CEMENT SURFACE FINISHES

http://talking-interior-design.blogspot.in/2015/06/cement-surface-finishes.html

Colour Palette

Colour Palette Flickr image by Rocco Lucia

20 CRAFT of WALL PAINTING (Neolithic)

http://talking-interior-design.blogspot.in/2014/02/the-craft-of-wall-painting-neolithic.html

21 CRAFT of WALL PAINTING (Palaeolithic)

http://talking-interior-design.blogspot.in/2014/01/the-craft-of-wall-painting-palaeolithic.html

22 COATINGS

http://talking-interior-design.blogspot.in/2013/09/coatings.html

23 COATINGS Iron age

http://talking-interior-design.blogspot.in/2013/09/coatings-iron-age.html

24 PRIMITIVE COATINGS Surfaces, Materials and Techniques

http://talking-interior-design.blogspot.in/2013/09/primitive-coatings-surfaces-materials.html

25 LIME-WASH

https://interiordesignassist.wordpress.com/2014/06/01/lime-wash/

26 PAINTING WHITE – 1

https://interiordesignassist.wordpress.com/2015/07/27/painting-white-1/

27 PAINTING WHITE – 2

https://interiordesignassist.wordpress.com/2015/07/29/painting-white-2/

28 BLACK Part – 1

https://interiordesignassist.wordpress.com/2015/08/07/black-part-i/

29 COLOURANTS DYES and PIGMENTS

https://interiordesignassist.wordpress.com/2014/07/15/colourants-dyes-and-pigments/

30 RED Colours of ancient times

https://interiordesignassist.wordpress.com/2015/05/22/red-colours-of-ancient-times/

31 ART COATINGS

https://interiordesignassist.wordpress.com/2015/05/25/art-coatings/

32 PRIMITIVE COATINGS # 1

https://interiordesignassist.wordpress.com/2015/05/03/primitive-coatings-1/

33 NATURAL IRON OXIDE PIGMENTS 4 # SIENNA and UMBER

https://interiordesignassist.wordpress.com/2015/05/01/natural-iron-oxide-pigments-4-sienna-and-umber/

34 NATURAL IRON OXIDE PIGMENTS -3 # Ochers

https://interiordesignassist.wordpress.com/2015/04/28/natural-iron-oxide-pigments-3-ochers/

35 NATURAL IRON OXIDE PIGMENTS – 2 # Red Oxides

https://interiordesignassist.wordpress.com/2015/04/27/natural-iron-oxide-pigments-2-red-oxides/

36 FLOOR PAINTS

https://interiordesignassist.wordpress.com/2015/03/21/floor-paints/

37 ARCHITECTURAL COATINGS -beginnings of OIL PAINTS

https://interiordesignassist.wordpress.com/2015/02/15/architectural-coatings-beginnings-of-oil-paints/

38 SURFACE PREPARATIONS

https://interiordesignassist.wordpress.com/2014/09/26/surface-preparations/

39 WHITE PIGMENTS

https://interiordesignassist.wordpress.com/2014/08/05/white-pigments/

40 CEMENT PAINTS

https://interiordesignassist.wordpress.com/2014/07/09/cement-paints/

 

640px-colourful_shoes_in_marrakech

Colourful Shoes Morocco Wikipedia image source > http://www.flickr.com/photo/cloudzilla/2718019182/ by cloudzilla

41 OIL BOUND DISTEMPERS -OBD

https://interiordesignassist.wordpress.com/2014/07/03/oil-bound-distempers-obd/

42 CEMENT FINISHES part 2

https://interiordesignassist.wordpress.com/2014/06/27/cement-finishes-part-2/

43 DRY DISTEMPER or CALCIMINE

https://interiordesignassist.wordpress.com/2014/06/03/dry-distemper-or-calcimine/

44 ECOLOGY and COATINGS

https://interiordesignassist.wordpress.com/2015/03/09/ecology-and-coatings/

45 ENCAUSTIC PAINTING

https://interiordesignassist.wordpress.com/2014/06/06/encaustic-painting/

46 COLOURS and BUILDINGS

https://interiordesignassist.wordpress.com/2015/01/20/colours-and-buildings/

47 GLOSS

https://interiordesignassist.wordpress.com/2014/09/20/gloss/

48 COMPOSITION of COATING

https://interiordesignassist.wordpress.com/2014/07/29/composition-of-a-coating-3/

49 COLOURED GLASS

https://interiordesignassist.wordpress.com/2014/08/03/coloured-glass/

50 GRISAILLE -monochrome form of presentation

https://interiordesignassist.wordpress.com/2014/07/28/grisaille-monochrome-form-of-presentation/

51 WATER COLOURS

https://interiordesignassist.wordpress.com/2014/07/10/water-colours/

52 FRESCO PAINTINGS

https://interiordesignassist.wordpress.com/2014/06/24/fresco-paintings/

53 PRIMER COATINGS

https://interiordesignassist.wordpress.com/2015/06/07/primer-coatings/

54 SINGLE or MULTI COAT SYSTEMS

https://interiordesignassist.wordpress.com/2015/05/30/single-or-multi-coat-systems/

55 BRUSHES

https://interiordesignassist.wordpress.com/2015/03/29/brushes/

56 ENAMELS

https://interiordesignassist.wordpress.com/2015/02/18/enamels/

57 TEMPERA

https://interiordesignassist.wordpress.com/2015/01/24/tempera/

58 GP -General purpose paints

https://interiordesignassist.wordpress.com/2014/08/26/gp-general-purpose-paints/

59 COLOURS -Perception and Expression

https://interiordesignassist.wordpress.com/2015/03/07/colours-perception-and-expression/

Acrylic Colours stux

Acrylic art colours Pixabay image by stux

60 EMULSIONS

https://interiordesignassist.wordpress.com/2016/01/30/emulsions/

61 CLEAR versus PIGMENTED COATINGS

https://interiordesignassist.wordpress.com/2015/11/29/clear-versus-pigmented-coatings/

62 SELECTING and APPLYING a COATING

https://interiordesignassist.wordpress.com/2015/11/27/selecting-and-applying-a-coating/

63 COLOUR MODELS (RYB)

https://interiordesignassist.wordpress.com/2015/10/14/colour-models-ryb/

64 BLACK Part – II

https://interiordesignassist.wordpress.com/2015/09/17/black-part-ii/

65 MASONRY PAINT FINISHES

https://interiordesignassist.wordpress.com/2015/11/17/masonry-paint-finishes/

Artists coloursby skeeze

Artists’ colours Pixabay image by skeeze

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PAINTING WHITE – 2

Post 485  –by Gautam Shah

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402px-Van_Doesburg_and_Rietveld_interior_1919

During 1930-50s Paint shops used to offer Oil-bound Distempers (OBD) and combination of Zinc pastes and double-boiled Linseed oil, for household painting. These were mixed with pigment pastes for shade creation. Post 1950s ready mixed oil paints or General purpose enamels (GP) became popular. But than paints’ shops had to stock several tins of different measures, for each of the shades and varieties (oil paints, distemper paints, flat and egg-shell plastic paints). And to match a desired shade, it was necessary to buy small bottles or vials of concentrated pigment pastes called tinters and top up an available shade or create one from a white.

Paint Shop of earlier era

There were two whites available, a ‘super-whitewith some form of ‘optical whitener or brightener, an ‘opacifier’ or colourants like blue or violet, and pure stuff called base-white, without any additives. Few lay people were aware of the later variety, or considered it to be some inferior stuff due to its less romantic name (super white versus base-white), and discounted price.

Zinc paste-based paints and General purpose enamels had linseed oil or its alkyd resins as the chief film forming material. The linseed has a tendency to oxidize and turn yellow over the age. This began to change due to strong demand from manufacturers of white-goods (consumer goods painted white such as ovens, fans, washing machines, refrigerators, etc.) for long-term non yellowing finishes. This led to use of non yellowing oils for resins, and new generation formulations of Urethane, Amino resins and epoxies. The same innovations began to percolate to home-paint markets. From 1960s Plastic polymer-based emulsion paints (called Latex paints in USA) began to be available. This offered non-yellowing white paints.

Shade Card

Titanium Dioxide as a whitest pigment had few technical problems of paint formulations, but these were initially solved with use of Zinc and Lithopone as additives. Oil paints in glossy and flat varieties, and Plastic Paint with, sheen, egg-shell-matt and flat varieties now were offered as one or two coat systems. This high hiding-covering was due to excellent pigment grinding-dispersion in machines like attritors that replaced ball and roller mills.

United States Capitol west front

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Paint markets are now radically changed. Paints manufacturing companies depend on shops to match the colour shades. The shades are created from basic, and few vials of ground pigments, which inject exact-micro quantity of colours into range of base formulations. The base formulations, include nearly clear to several types of white paints. White bases have natural shades of white pigments, and some have whitening-opacifiers. A white base is used for light tints, but not more than 100 ml paste can be added for darker shades to avoid loss of gloss or the effect on drying time. A neutral, pastel or mid-base contains lesser quantity of white pigment and is used for creating darker colours. And a clear base is used (it may contain white powders of low refractivity or extenders, but is free of high refractivity white pigments), for very deep colours. Some manufacturers use this base to add little sheen to matt paint.

Whites are affected by surroundings and show many variations

Whites are affected by smallest amount of additive colourants. These colourants may come from residues of earlier colour in brushes or rollers, any loose particles on the surface to be painted and thinners (solvents and water). Some additive colourants, if not thoroughly mixed, begin to darken the colour shade over brushing or rolling. Extra ordinary care is required in selecting, buying, mixing and using, white and ‘off-white’ shades. Shops have a file of colour shade cards, which are rarely fresh. The shade card viewing must be done in natural light, as it is affected by the surroundings and type of illumination. Shop computer calibrated and mixed shades, are not necessarily exactly right as per the shade card or as per your need.

A colour shows many variations at different angles of viewing and so colour matching must be done perceiving it from as many positions > Pic by https://www.flickr.com/photos/horiavarlan/4271993197

One of the best ways is to buy a small trial pack, and apply it on two different walls (preferably at right angles), at the site location. Once a right shade is achieved, leave some quantity (see the next paragraph) in the trial pack for master batching and matching.

HOW to mix a white shade with very light tinge of other colours at home? Buy the most appropriate white-base out of several ones available at a paint shop (usually 2-6 varieties). Now separately mix the concentrated tint to small quantity of white-base, with shade as close matching to your desire. Such faint tinges of colours are very difficult to visually perceive. So place a drop of experimental mix over the quantity left in trial pack. Your shade will be either darker or lighter, but easily perceptible.Mixed Whites

Most plastic emulsion paints now have a ‘Thixotropic’ compound, which gives a heavy, butter like false viscosity to the paint, to prevent separation or settlement of heavier phases or solids. Stirring is required to reconvert the stuff to a temporary liquid phase. Plastic paints come with good odours, to suppress the unpleasantness of paints, but one need not judge a paint on that count.

Color Blue Church Terrace Architecture White

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PAINTING WHITE – 1

PAINTING WHITE – 1

Post 483  by Gautam Shah

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Painting anything white is easier said than actually achieved. Lovers of white are like ‘platonic lovers’ and so are confused as to what colour needs be used. The sensual lethargy arises because there are too many tinges, chroma, hues and tones of colours in the market to select from, and earlier affairs have been disappointing. Some lack the daring to experiment, or incapable of orchestrating coordinated response with the variety. And to this, the response is extremist, not only white is sought, but want whitest white and everywhere. The maddening craze cannot be achieved on own, through a painter, or a novice designer. It needs help of a person of experience with technical know-how.

White Sands Pensacola Beach, Florida USA

A white colour seems different to different people, in specific environmental conditions, spatial settings, and most importantly in presence of other colours, in proximity or even memory. There are many examples of whites around us, Clouds, vapour, milk, flowers, teeth, bones, cotton, snow, swans, ducks, rabbits, and skies. Then why is it so difficult to colour anything white? Nature has provided one of the most abundant materials to create the white, Lime or Calcium Carbonate. There were several other minerals like China clay or Kaolin (so-called after the towns of Gaoling or Kao-Ling in Jiangxi province, China), Magnesium carbonate (Magnesium was first discovered outside of the Greek city of Magnesia), Talc, Diatomaceous earth, Marble dust, etc.

White Cliffs of Dover

 A white is effective due to the high refractive index. Lime powder and gesso (China clay, gypsum), were the first whites available in prehistoric times. These were used for levelling the surface and for creating a white ground. As per the modern day terminology both the materials are not white pigments, but extenders. A white pigment has refractive index, above 2.0 (Titanium Dioxide Rutile grade -2.73, Titanium Dioxide Anatase grade -2.55, Antimony Oxide 2.09-2.29, Zinc Oxide -2.02, White Lead basic Carbonate 1.94-2.09), where as most extenders have refractive index range of 1.65. This in very simple terms means that a white colour will have low covering-hiding capacity and so seem ‘dull’ or transparent white, if entirely or partly made of extenders. A white colour of Titanium Dioxide will seem ‘full’ or opaque white.

by JJ Harrison (jjharrison89@facebook.com) Wat Rong Khun, Chiang Rai, Chiang Rai Province, Thailand

Pigment Volume Concentration -PVC is relative proportion by volume of pigment to a resin (binder). Glossy paints have lesser volume of (17%) pigments compared to semigloss 25 % and flat paints can have 38-40 %. It is preferable to use a flat paint over fresh plaster, as it levels the surface better, but a flat paint on a virgin surface may look extra flat, due to greater absorbency.

Pic by Luc Legay on Flickr > Fascination of all White party

Lead white was used by artists and decorators for several centuries in spite of its known toxicity. Greeks called it Psimithium and Romans Cerusa. Most of the older classical oil paintings were created over a lead white canvas primer coat. White Lead or Basic Carbonates pigment in linseed oil paints offered good adhesion and brush-ability and so was used for creating highlights in canvas painting. Zinc oxide, was known as a medical material for open wounds as mentioned in the Indian medical text ‘Charaka Samhita’, from 500 BC or before. Zinc white was accepted as a pigment for linseed oil-based paints for paintings by 1834. Lithopone is a white pigment, a mixture of barium sulfate and zinc sulfide. It was used as a substitute or supplement for toxic white lead.

National Library of India Calcutta

Titanium Dioxide as a white pigment was discovered in 1821, but its commercial use as pigment began in 1921. It has a tinting strength far superior to any other white. In artistic oil pastes, it dries to a spongy film, so needs to be mixed with Zinc or Lithopone. Cheaper brands of paints or Oil bound distempers (OBD) often use titanium dioxide mixed with barytes or other pigments, but at the cost of brilliance and tinting strength. Titanium dioxide ranges of pigments are nontoxic.

Oia Santorini Greece

To be continued to Painting White -2

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PRIMITIVE COATINGS # 1

Post 411 – by Gautam Shah

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Coatings have been used for decorating and suffusing objects and surfaces for the past 60000 years. These were used for several purposes such as to add a colour, impart a protective layer, ‘plaster’ a surface, imprint a pattern or create an identity signage.

Stone and other artefacts requiring coating or decoration

A primitive person had many objects that could receive the coatings. These objects were natural, reformed or produced ones. The objects had different sizes, shapes and surfaces. The surfaces had characteristic textures, porosities, base-colours and patterns (grains, patches, stains, etc.).

Korea Neolithic age pot

The objects were own body skins, hairs, and nails. Animal products like teeth, animal hides, furs, bones, and teeth. Minerals’ items like sands, clays, stones, rocks, precious stones, and sea shells. Plant items such as dry leaves, grasses, seeds, dried fruits, fibres and woods. The manufactured range of items included clay products, ceramics and metals.

sesklo

The surfaces were prepared to receive the coating. Hides were cleaned and shaved by heavy rubbing. Body surfaces were oiled to receive the colourants. Walls were washed and wetted prior to coating application. Bones were ground to remove the sheen and make surface slightly rough and absorbent. Stones and woods were polished or scrapped. Raw and baked clay products were re-fired after coating. Leaves were rolled and flattened and dehydrated at the green stage by burying in layers of ash or sand.

The coatings’ materials were of natural origins, such as available off the ground, or from animals and plants. But the coating materials were processed by filtering or sieving, washing, cleaning, decanting, boiling, singeing, and sintering.

The act of coating was intentional, done with a sure purpose. But the resultant effects were wondrous, something that gave a new purpose to the artefact. The art of drawing and the technique of coating, was seamless process of magic. A process to express, what the postures, gestures or spoken language could not do.

Coating techniques and materials of the primitive age are still being used in many situations, and so continue to be relevant. Blood is perhaps the earliest colourant, as a fresh liquid it has very rich colour. It was a colour to represent the vibrancy of life and metaphorical power over the kill. Blood, however, is biologically degradable material, dries to a darker shade, and has very weak colour-integrity. Wood coal is a dry colourant, easy to handle. It requires a textured base for ‘rubbing-in’ or a binding liquid to form an applicable paste. Carbon (Lamp) black -a deposition collected over burning fat or oil, is much better due to oil content. Whites were procured from metallic oxides and carbonates. Lime is most common everywhere. Other whites included talc, whiting and barytes. Iron oxides are equally common, and have many different hues (such as yellow ochres, browns of sienna and umber, red and black oxides). Oxides are very stable, and have ‘deep’ saturated colours.

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Black Carbon of Soot or Lamp black

In this palette of colours, the notable absence was Blue and Green. Blue and green appeared very late in the form of Lapis lazuli and Malachite (copper carbonate hydroxide). Brilliant Red that could represent the fresh blood, and Brilliant Pink of the meat were also absent. Purple was nearly unknown. The absentee colours were sourced from plant juices and natural dyes, but had poor colouring strength or low opacity (transparent), sun light fading, and biodegradable colours so were not long lasting.

Sprayed colours

The primitive colourants were mostly of dry powders or soft rocks. These had no binding capacity. Mineral pigments were heavily rubbed on the surface to trap them in the micro cavities of the surface. Liquid juices could absorb into the surface. Some form of binding material or technology was needed. Water has temporary binding capacity and can be used as a carrier agent. To fix colours plant oils, mutton fats, fish oils, etc. waxes, and plant latexes were used. These substances except the wax were ‘non-drying’ and remained wet for a long time. The wet surface attracted dust and trapped insects. The oily substances biologically deteriorated, and on oxidation turned darker in colour.

Proteins-based materials like blood, eggs, milk, urine, and starches were also used as binding materials. Plant and insect exudates or natural gums had binding properties but were highly hygroscopic (affinity with water) materials. Plant milks or latexes, like materials, were also used. Wax was used to mix with pigments and as a protective layer. Wax and natural Creosote were used to protect wood and leather surfaces.

Number of cementing substances were used for coating or plastering. Mud plasters, slaked lime and Pozzolana (volcanic) ash, were materials that had binding properties. Colouring these substances, or coating over it (fresco style) required large quantities of materials, or concentrated pigments. Lime when mixed with a colourant imparted a white shade creating a ‘pale’ effect. Pozzolana had darker colour so made the colourant several shades darker. Plastering and daubing, were frequently used to prepare a better surface for a wall painting. Primitive binding materials can be categorized like, 1 Materials that are water reducible, water resistant and hygroscopic, 2 Air drying and non drying, 3 Non water-based materials.

ancient_azerbaijan_4

The primitive age craft of coating can be summed up as 1 Surface preparation, 2 Application of the coating, 3 Applying tonal variations or shades, and 4 Covering the surface with water protective coat, usually of oils or other transparent materials. The process of application of colourants or the coating system was adapted to the nature of the base surface, as much as to the type of colourants and binders.

Twig brushes

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Drawing points and crude shading brushes

Primitive coating applications are varied. The simplest way of marking cave walls art was to make finger-nail traces in the soft layer of clay covering the rock. Lime stone walls were engraved and filled in with iron oxide (Hematite, or ochre), or the black pigment such as the manganese or charcoal. Analysis of cave wall art pigments, reveal the use of extenders (dull or low opacity powders) such as talc or feldspar, to increase the bulk of pigments. The coating also shows traces of animal and plant oils, used either for binding or as a protective covering. The pigment in paste form was applied with fingers, and also tools like fiber pads, animal-hair brushes or crushed twigs. Lumps of pigment discovered on the floor of caves were perhaps used as crayons, or were grinding onto colour powder. Colours were often sprayed, from the mouth or through a tube. A network of ladder, supports and scaffolding was used to reach the ceilings and upper portions of walls. Light was provided by hearths, or portable burning torches. The coated surfaces were ground to achieve a sheen on the surface or re-coated with a protective layer of egg-whites, oils or fats.

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The earliest known use of colourants dates back to 70000 years, whereas Cave wall art is about 40,000 years or older. BC. Lascaux, an underground cave, 17300 BC, located in SW France, has walls and ceilings, decorated with some 1,500 engravings and about 600 paintings in shades of yellow, red, brown, and black. The subtle tonal gradations of colour on animals painted in the Altamira and Lascaux caves appear to have been dabbed in two stages with fur pads, natural variations on the rock surface were exploited to create the effects of volume.

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NATURAL IRON OXIDE PIGMENTS – 1

NATURAL IRON OXIDE PIGMENTS – 1

Post 406 – by Gautam Shah 

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Iron Oxide ColoursNatural Iron oxide pigments are some of the most commonly available colourants, nearly everywhere on earth. There are as many regional, as there are local colour variants, offering a vast palette of colours ranging from nearly black, to red, brown, etc. Natural Iron oxide pigments are very stable (chemical reactivity), sunlight fast (UV radiation), nontoxic, and remain unaffected by moisture or heat (up to 550C for red oxide and up to 105C for yellow oxides). Iron oxides are resistant to oils do not react readily with solvents.

Queen Nefertiti

Iron-oxide pigments are extracted from many different types of ores such as Hematite (reds), Goethite and Limonite (Yellow-browns), Siderite (brown-reds), and Magnetite (blacks). Red hues are attributed to hematite Fe2O3, Yellows to hydrated oxides of iron, and Browns to MnO2 or black impurities. The pigments consist of Ferrous or Ferric oxides, with impurities such as clay, silica, calcium carbonate, manganese, etc.

Iron oxide Yellow pigments are based on iron oxide hydroxides are referred to by many different names, including goethite, limonite, raw sienna, Mars yellow, yellow earth, yellow ochre, yellow iron oxide, yellow hydrated oxide and iron hydroxide pigment. Iron oxide Red pigments are based on anhydrous iron oxide, and referred to as hematite, red oxide, rust, red ochre, burnt sienna, Mars red, etc. Iron oxide brown colours are mainly based on Manganese oxide or pyrolusite are brown yellow oxide, ochre, umber, burnt umber, etc. But many colours are more known by the locations of the extraction, as seen by names such as Venetian red, Sinopia, Turkey red, Indian red, Spanish red, Pompeian red, Persian red, etc.

Lascaux

Oxide colours have retained their fascination mainly due to the stability and consistency. Red and Yellow oxides were two shades that have survived in caves for nearly 70000 of years. The advantage of red oxide offered was against the most commonly known red colour of the blood. But colour of the blood turns brown on drying and is highly susceptible to biological degradation. Blood colours are translucent and are not comparable to red of the oxide colours. Black was used in cave paintings, but its source the carbon (lamp) black offered very fast, intense and indestructible shade. Even the occasional (in few regions) use of Black iron oxide is no match for it. Black colour was also made by reacting Iron with an acidic substance. Another natural red colour was the Indian vermilion, made by reacting turmeric with an acid.

 

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Oxide colours were used for body decoration. Pigments grinding equipment believed to be between 350,000 and 400,000 years old has been reported in a cave at Twin Rivers, near Lusaka, Zambia. The technology of refining by way of cleaning, washing, sieving and grinding, and calcining is very ancient. The naming of oxide colours as raw or burnt for ochre, umber or senna, was familiar to all artists for ages. By heating or calcining the oxide colours became intense or rich.

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Namibie Himba Oxide body colour

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Before the Industrial Revolution, the range of colours available for art and decorative uses were limited. The range consisted earth or mineral pigments or colours of biological origin. At places colourants from unusual sources such as botanical materials, animal waste, insects, etc. were used. The colour range was sought to be enlarged by purification, mixing with other colours and chemical treatments.

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It was realized by artist that the range of hues and tones offered by Iron Oxide colours is limited. During the industrial revolution period efforts began to produce very large and consistent quantity of synthetic equivalents.

The son of a master dyer, Tintoretto used Carmine Red Lake pigment, derived from the cochineal insect, to achieve dramatic colour effects.

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ECOLOGY and COATINGS

Post 359 – by Gautam Shah 

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Coatings (Paint, Varnish, etc.) consist of organic as well as inorganic substances. Both the categories of materials can be hazardous at several levels such as: production, application, curing or drying, functional use, and disposal level.

Claude Monet Waterloo Bridge London

At production level the handling and use of certain raw materials can be hazardous. Typically handling of extenders and pigments can pose air-bourne particle spread. Some of these silica containing materials are toxic and carcinogenic and not eco-friendly. Resins (amino) with styrene and formaldehyde are carcinogenic. Solvents are known fire prone materials. At application level, the primary hazard occurs, due to high amounts of volatile organic content going into air. Its vapours or odours are noxious, allergic and unpleasant. The odour suppressants added to coatings are not necessarily benign. At application level, old coated surfaces are rubbed or scrapped, the particulate matter of which causes air pollution and the constituents are often unfamiliar.

Aerosols cause high level of air pollution

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Post application, the wearing surfaces and peel-off cause, dust pollution. Some of the plastic materials continue to deteriorate, evolving pollutants. Coatings used on kitchen shelves, utensils, equipments cause contamination. Accidental high heating and fire scorch a coating. Planned removal of coating by sanding and chemical etchings (paint scrubbers or removers) can also leave unwanted residual products. Disposal of coated items by sawing, forced removal, hammering, chiselling, sanding, scrapping, etc. can desecrate the environment.

PIGMENTSClay colours

Prolonged or high intensity exposure to paint and paint fumes can affect three main organs, lungs, kidney and lever. These manifest as headache, allergies and asthmatic reactions, irritation of skin and eyes, burning in nose, airways, urinary tracts.

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The trend world over is to design entities with their own or integrated surfaces. A variety of metal and polymer surface treatments are available that molecularly change the quality of the surface. Such `surface systems‘, rather than `surface finishes‘ often do not require any application of foreign substances. A variety of single or a combination of treatments like temperature, radiation, sonar, mechanical finishing, stress induction and relief, cathodic protection etc. can eliminate organic coating systems. Such surfaces do not have any applied finishes, but rather have a generated finish.

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There are many inorganic coating systems that are akin to metallizing systems. In such systems the role of medium is to carry and spread the pigment and other substances. On baking or firing the medium is evaporated or burnt off leaving metallic or alloying compounds on the surface. Such substances are generally heat or flame cured to cross links with the substrate material.

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