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[BKARTS] Paste Debate!



Greeting Everyone,

I would like to re-open what may seem to be an old topic for everyone; the particular qualities of starch paste adhesives.
Over the years, I have heard a great deal about wheat starch versus rice starch. Searching the list archives, I found information on what constitutes starch, how it differs from flour, how starch is separated from gluten, and various preferred methods of preparation. For now, I would like to reconsider rice vs wheat, and then perhaps as a subtopic, the various qualities of Aytex P, zen Shofu, "pre- coooked" wheat, the cheap starches obtained from Asian grocers, and why not Softasilk cake flour while we're at it. Oh, and let's not forget precipitating your own starch from flour.


For some time I have been told that rice starch molecules are much larger than wheat, engendering greater tack and rigidity in dried rice paste films.
The smaller molecular size of wheat supposedly engenders greater flexibility. Just now, I read that wheat is actually "polymodal", meaning that the molecules can vary in size. Perhaps this has something to do with the molecular size of these molecules, but I also wonder if the source of the starch (specific species of wheat or rice) may influence these factors, as well as the ratio of amylose and amylopectin.


In addition, I have been told that an artificial aging test showed that rice can become yellow and brittle over time. On the other hand, I am also told it maintains a higher Ph than wheat starch paste. What about combinations of starch pastes, or the addition of methyl cellulose (HPMC, such as Dow E4M) Maybe we should be exploring kudzu (kuzu) starch for our purposes?

Rather than invite a plethora of comments about what one personally prefers to use or believes to be "superior", I would love to see published sources that can be cited, as very few sources are mentioned in the list archives. In addition, to promote a civil tone in the discussion, I would just like to mention that I personally believe that each adhesive has their place; there is no "bad" adhesive; only poor choices of application. The place for some adhesives may not be in conservation or book art, but it may very well be good for something else (such as in the kitchen). Similarly, I also do not subscribe to the idea that "one size fits all". An adhesive used for the most delicate paper conservation may not be the most suitable for leather binding and vice-versa.

Thanks!

Jake Benson

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