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Hi, I'm new to this but have a lot of experience in ceramics, as does my internet friend. She sent me this papier mache recipe, after trying it out and says it's good (we are both interested in moving into papier mache for various reasons). However, it requires potato starch which seems expensive.. can I just swap it for powdered wallpaper paste without changing the properties?
The recipe she gives is as follows, and she calls it a 'Mongolian Papier Mache' recipe:
newspaper
whiting (this is the potter's source of calcium carbonate and very cheap indeed)
potato starch
a big old saucepan
All ingredients are in equal parts (although she seems to contradict this by adding more whiting later on in the process).
Tear the newspaper into strips, add boiling water to get a fine porridge consistency. Add potato starch and whiting, boil for a couple of hours and leave overnight. Come back to it in the morning and shape the paste into sticky balls. Knead more whiting into the balls to get a soft dough consistency. Voila!
All ingredients are used in equal parts, but from what she's written to me, she's pretty relaxed about proportions. I'm not sure how she weighed/measured, I'm assuming by volume.
So yes, this is a long post just to ask whether I can swap potato starch for powdered wallpaper paste, but if you have any general advice on this recipe that would also be appreciated! Thanks in advance!
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Well, that is interesting. I have never added the calcium carbonate during the boiling process, always once the paper pulp has been well mixed with paste, which makes it easier to ensure that the mix is not any wetter than necessary.
When I have enquired about the manufacture of wallpaper paste (UK), I have been told that it is based on potato starch (not CMC) so it should be perfectly OK.
I always add about 25% PVA to my paste and find it good, though Sue (catperson) scoffs at it!!
So, yes, I think you'll be fine with wallpaper paste.
David
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Thanks dopapier, I'll go with adding the calcium carbonate after the boiling process - being potters, we like to mix things wet (in ceramics most powders are suspended in liquid and finely sieved to achieve consistency). It's probably just a hangover from that mentality.
Would you add 25% PVA on top of the wallpaper paste, mixing it in by hand along with the calcium carbonate? I see the logic in adding it - just depends on the desired final strength I suppose.
Another thing that potters to for optimal workability and adhesion is to add fibers to clay in tiny quantities (0.25% makes a huge difference in everything from ease of modelling/joining to better drying, crack resistance during drying and also finished dry strength. Too much actually decreases workability but small amounts improve it) - it would be quite advanced to add 1/4 inch nylon fibers and maybe unnecessary, but thought I'd mention it.
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Here in the U.S. (and I suspect the UK isn't any different) there are four forms of wallpaper paste: (methyl) cellulose-based (usually made from wood or cotton), flour-based (usually made from wheat, potato, corn or rice), vinyl-based, and vinyl-clay based.
I don't have any experience with the vinyl-based kinds, but the advertising says that the vinyl/clay type is used when "superior tack" is required. Both of these are pre-mixed in tubs. Personally, I would advise caution if using any vinyl adhesive for heavily built-up papier mache of considerable thickness. I personally viewed a disaster that was about 1/2" thick. It never dried -- ever. Apparently, the outside dried first, and sealed the inside from the air.
The flour-based ones are milky-looking when mixed with water, and are the cheapest of the wallpaper pastes. They are often/usually cooked to make a better paste. Leftover paste must be refrigerated or it will mold quickly. It will last almost a week in the refrigerator (if it smells bad, throw it out). It can attract insects, rodents and dogs (mine, anyway), and even after proper drying, it will re-absorb moisture from the air if not sealed. 1 lb costs approx $5USD.
The (methyl) cellulose types are clear, and the price here is approx. five to six times the price of the flour kinds. It MUST be mixed with cold water. You can use less paste with more water, so it goes farther, and it dries faster than the flour type. It doesn't re-absorb much moisture from the air.
It is so highly processed that it doesn't seem to mold at all, even at room temperature. 1 lb costs $22-28USD.
It's fun to try all kinds of adhesive mixes, but I would advise making it in small amounts to see if what you get is what you wanted. Sometimes you get... ah... 'surprises'.
Just remember that all flours can be added to HOT water and cooked if you want to. All CELLULOSE ones must be mixed with COLD water.
Sue
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