A few years back, I made my own wheat starch just because I wanted to do the process by hand, in a traditional method.
The last part of the process, before drying, involves letting a fungus or mold form on the surface of the water and allowing it to send tendrils to reach several inches down into the water and feed on any remaining gluten, etc, leaving only the starch behind.
The water is changed often enough that the fungus/mold does not get out if hand and you know the job is done when no growth forms, because there is nothing to feed on.
It is a long process but in the end you have a material that has most, if not all, growth medium for nasties, removed.
So, if you do not use acrylic medium for a glue, I recommend that you buy some dry whole wheat for making paste.
My 2¢.
Eli
>Yes paste has a bad rap for several reasons.
>Here’s a compilation from the Book Arts List:
>
>
http://cool.conservation-us.org/byform/mailing-lists/bookarts/2006/07/msg00131.html
>Supposedly it changed its formulation but the latest information I could find till had it being made of dextrin and corn syrup - neither of which are things you really want around your art works as they are likely to develop mould or attract bugs for a quick meal...
>More info below:
>
>From MFA-CAMEO (a great materials site), here’s a breakdown:
>
>Material Name: Yes Paste
>Description
>A brand name for a starch paste formulation that also contains corn dextrin, corn syrup, and a preservative. The all-purpose adhesive is acid-free and non-toxic.
>
>Other Properties
>Water-based. pH = 6.5
>
>
>Information on the components of Yes Paste:
>
>Material Name: dextrin
>Description
>A water soluble polysaccharide produced by the hydrolysis of starch. Patented in 1867, dextrin is produced when starch is hydrolyzed with dilute acid and heat, then neutralized with alkali. Pure dextrin is a white, amorphous powder that has a sweetish taste. It is used as an adhesive for envelopes, gummed paper, postage stamps, and mounting photographs. Dextrin is also used for sizing paper and textiles, for printing inks, as a thickening agent, and as a paint binder in poster paints and cheap tempera colors. Dextrin is sensitive to moisture, weathers poorly, and is susceptible to biodegradation. Two forms of impure or partially hydrolyzed dextrin are also available:
>- British gum: a dark, brown powder that forms a tacky adhesive in warm water.
>- Canary (yellow) dextrin: a water-soluble yellow powder.
>
>Synonyms and Related Terms
>dextrine (AAT preferred); starch gum; amylin; British gum; gommeline; vegetable
>gum; artificial gum; leiocom; sago dextrin; tapioca dextrin; canary dextrin;
>starch syrup; Dextrine (Deut.); dextrine (Fr.); dekstryna (Pol.)
>
>Other Properties
>Soluble in hot water. Insoluble in ethanol, ether.
>
>Fluoresces a blue-white in ultraviolet light.
>
>Iodine gives a red to blue color.
>Last updated on: 3/7/2006 6:09:18 AM
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>
>Material Name: corn syrup
>
>Description
>A viscous, sweet liquid obtain from the hydrolysis of cornstarch. Corn syrup is commercially used as an inexpensive sweetener in baked goods, jams, jellies, candies, juices, and soft drinks. Corn syrup has been used as a plasticizer in glues and starch pastes. It is less expensive than glycerol and it does not crystallize with age like honey.
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>Synonyms and Related Terms
>No synonyms found.
>
>Hazards and Safety
>Corn syrup can attract insects and is susceptible to biological growth.
>
>
>Cheers,
>Lee