Know your gums

Know your gums.
No not the type that hold teeth; the ones that you can add to your icing to make figures and flowers. Gums, are thickening agents that help make figures and flowers retain their shape and dry hard. Some, like gum arabic, can also be used to add a realistic shine to your finished item - eg leaves and berries.

Gum tragacanth is a natural gum that occurs in legumes found in the middle east. Over the years it has been used in artists paints, leather tanning, medicines, and as thickeners for foods (additive number E413). 
It hasn't been grown outside of the middles east commercially, as there are other cheaper gums available. Due to where it is grown, supply is often interrupted by the various conflicts, and trade sanctions that occur in this region, which affects price and availability. It can be consumed by all religious and dietary groups.

Carboxymethyl Cellulose ( or CMC powder additive number E466. Also known as Tylose powder) is another type of gum that is commercially available and is significantly cheaper than gum tragacanth. It is obtained from wood pulp and/or cotton and then chemically altered to make it water soluble. It isn't digested by the body and is used in diet drinks and foods. It is used widely in the food industry as a thickener and also in medicines (eg fake tears), textiles etc. During the manufacturing process, salt is produced (sodium carboxymethyl cellulose) which is spearated from the white CMC. It can be consumed by all religious and dietary groups.

Gum Arabic (additive number E414) is produced when the bark of certain types of African acacia's is damaged and the tree seals the wound. It is mainly grown in the African Sahel.
It has been known for thousands of year and used in cosmetics, mummification, food thickeners and stabilisers, calligraphy and artists paints.
Gum arabic can be used to 'seal' sugar pieces and prevent damage through humidity, but leaves the piece with a shiny finish.
It can be consumed by all religious groups dietary groups.

References:
http://www.food-info.net/
http://www.lamberti.com/technologies/carboxymethilcellulose.cfm
http://en.wikipedia.org/wiki/Gum_arabic