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Gum arabic is a natural gum made from the hardened sap of the acaia tree. It is a complex mixture of polysaccharides and glycoproteins. Acaia gum is used in pottery and ceramics, as a gum in photography, in printing, paint production, glue, cosmetics and various industrial applications. As a gum it helps to increase and control viscosity of aqueous solutions and is commonly used in the inks and textile industries.
In pottery and ceramics it is used in water as a medium for underglaze colours and in glazes as a binder. For artists Gum arabic is added to water colours to improve the gloss, brilliance and transparancy of the colours. It is normally added as a few drops to the mixing-water. It also acts as a binder for the pigments to the paper when the water evaporates. Other uses include lithographic printing, pyrotechnics, manufacture of polishes and adhesives.
An adhesive can be produced by mixing 1 part of acacia gum with 5 parts of hot water.
Properties of Gum Arabic:
PLEASE NOTE: This product is not for human or animal consumption.
Painting and art
Powdered gum arabic for artists, one part gum arabic is dissolved in four parts distilled water to make a liquid suitable for adding to pigments.
Gum arabic is used as a binder for watercolor painting because it dissolves easily in water. Pigment of any color is suspended within the acacia gum in varying amounts, resulting in watercolor paint. Water acts as a vehicle or a diluent to thin the watercolor paint and helps to transfer the paint to a surface such as paper. When all moisture evaporates, the acacia gum binds the pigment to the paper surface. After the water evaporates, the acacia gum in the paint film increases luminosity and helps prevent the colors from lightening. Gum arabic allows more precise control over washes, because it prevents them from flowing or bleeding beyond the brush stroke. In addition, acacia gum slows evaporation of water, giving slightly longer working time. The addition of a little gum arabic to watercolor pigment and water allows for easier lifting of pigment from paper and thus can be a useful tool when lifting out color when painting in watercolor.
Gum arabic has a long history as additives to ceramic glazes. It acts as a binder, helping the glaze adhere to the clay before it is fired, thereby minimising damage by handling during the manufacture of the piece. As a secondary effect, it also acts as a deflocculant, increasing the fluidity of the glaze mixture but also making it more likely to sediment out into a hard cake if not used for a while. The gum is normally made up into a solution in hot water (typically 10–25 g/litre), and then added to the glaze solution after any ball milling in concentrations from 0.02% to 3% of gum arabic to the dry weight of the glaze. On firing, the gum burns out at a low temperature, leaving no residues in the glaze. More recently, particularly in commercial manufacturing, gum arabic is often replaced by more refined and consistent alternatives, such as CMC.
The historical photography process of gum bichromate photography uses gum arabic mixed with ammonium or potassium dichromate and pigment to create a coloured photographic emulsion that becomes relatively insoluble in water upon exposure to ultraviolet light. In the final print, the acacia gum permanently binds the pigments onto the paper.
Gum arabic is also used to protect and etch an image in lithographic processes, both from traditional stones and aluminum plates. In lithography, gum by itself may be used to etch very light tones, such as those made with a number five crayon. Phosphoric, nitric or tannic acid is added in varying concentrations to the acacia gum to etch the darker tones up to dark blacks. The etching process creates a gum adsorb layer within the matrix that attracts water, ensuring that the oil based ink does not stick to those areas. Gum is also essential to what is sometimes called paper lithography, printing from an image created by a laser printer or photocopier.
Gum arabic is also used as a water-soluble binder in fireworks composition.