You are not logged in.
As you already are aware there are zillions of variations on preparing paste for PM. Many include the use of flour and some of them involve cooking it through boiling while others either don't cook it and some do include flour altogether.
I recognize that flour forms the 'glue' in recipes that do not include PVA in the mix but what is the effect of cooking or not. I would venture to guess that cooking breaks down some of the molecular structure, but if you don't cook it, how does it affect the integrity of your project.
If I am wrong about assumptions please correct me.
While I'm at it, I saw one recipe that mentions sugar; what does that do?
Offline
As I understand it, cooking helps activate the gluten (think the stringy-ness that forms in bread dough when you pull it apart.) That adds strength to the glue. So non-cooked is still glue, but without the reinforcing strings of gluten.
In my paste, which is mostly methyl cellulose, I add a small amount of white glue (PVA glue) with laundry starch which forms long-chain polymers. When mixed within the methyl cellulose ... it gives a similar stringy-ness effect.
Uncooked flour and water paste is what Dan Reeder uses, however ... it does add a hardness (I think from the undissolved flour) ... `
-- b
Offline
Thanks 'b'
That make a lot of sense in terms of gluten and polymer chains. What do you consider to be the key benefit in using Methyl Cellulose? Can you share a paste recipe and where do you source it?
koko
Offline
The most common source of Methyl Cellulose is Elmer's Art Paste. Pretty readily available at most art stores or on Amazon. A box is under $5 and mixes up a gallon. Other sources are book binding supply companies.
Joey
Last edited by paper soup (2012-11-13 00:31:02)
Offline
I just found the David Osborne article on this site (http://www.papiermache.co.uk/articles/p … che-paste/) and it has a wealth of info on methyl cellulose. Thanks PS, I'll look for the Elmers
Offline
koko,
Elmers art paste works fine, but I'm partial to Dow's Methocel A4M which I get in College Park at Bookmakers ... http://www.bookmakerscatalog.com/catalo … esives.htm
Because I pick it up, I don't pay shipping charges, and without the shipping it's close enough in price, that I don't worry about the difference. (One 1/2lb container makes about 2.5 gallons of paste).
[My recipe used to be 6 MC : 1 Glue : 1 Starch ... it still is if using white glue other than 'Elmers New Improved' ... the new improved version of Elmers has more solids so it reacts more to the starch. I now add only 1/3 part of starch to 1 part Elmers, and start with 6 parts MC, adding more to get the desired consistency if needed. ]
Methyl Cellulose is used as a coating agent in foods / medicines. My theory about what's happening in my paste is that when I mix the white glue and starch forming the long-chain polymers ... that starts to clump like melted cheese ... so initially I have a big wad of glue and starch around my stirring stick. But as I continue to stir it smooths out and disperses -- leaving me with glue that resembled stringy egg whites.
The egg white consistency spreads easily -- allows me to slide pasted papers if I need to adjust something, and dries with a little more reinforcement from the polymer chains -- which reinforce the locking paper fibers themselves.
That's my theory anyway. Haven't looked at any of it under a microscope, but I did do comparison tests when I was first testing glue recipes ... and liked this one the best.
I hope that answers your question ... if not, ask again. : )
-- b
Last edited by bmaskmaker (2012-11-13 17:23:05)
Offline
Have a look at my article about Paste. It may answer your question regarding the use of flour.
DavidO
Offline
Cooking makes flour-based adhesive stickier. Without the heat, the tiny bits of flour just sit there, but with the addition of heat, they swell and get stickier.
It's simple and nontoxic, as long as you don't have creatures around that would be attracted to a food product. Don't dawdle -- get your project made, dried, decorated and sealed. Keep it out of the reach of pets. *rolling eyes*
Sue
Offline
B,
How much actual paste does a half pound of that methyl cellulose make?
Offline
Paper soup: a lot. The usual recipe is 1 Tbsp. MC mixed into 2 cups of cold water, and let set a few hours or overnight. DO NOT use hot water!
Sue
Offline
Thanks Cat,
I have used the Elmer's and did like the texture and results. I just usually work on such a large scale that I find mixing and waiting tedious. I may order some of 'the good stuff' and try some pieces on a smaller scale. Generally my larger theater pieces don't need to last forever anyway. Props are rather ephemeral. 
Joey
Offline
Paper,
I make my batches in those 1/2 gallon Mix-A-Lot buckets ... and I get about 5 1/2 batches (so ~ 2 1/2 Gallons). And, like the Elmers version, as long as your bucket is clean it doesn't 'go bad' because there's nothing in it to spoil. (Once I mix my paste which has some laundry starch, that can go off, but straight methyl cellulose lasts a really long time.)
It comes in different viscosities. I get the A4M which is more viscous ... I find that saves me a bit, because I can thin it with water if I want/need.
: )
-- b
Last edited by bmaskmaker (2012-11-24 20:55:07)
Offline
If you make up a big batch of MC, be sure you cover it for storage. I accidentally set a cup of it on a shelf and discovered it about 3 months later. It had dried to a gummi bear consistency. I didn't try reconstituting it, so I didn't know if the layer of dust and cat hair on the top would have been of any benefit or not.
Some day, I will try adding a thin film of discarded (by the cat) cat hair between strip layers and see if it adds strength.
Sue
Offline
: )
Yes, definitely covered. I tried to see if I could use dried mc as a clear casting material and left some to dry in an ice cube mold. Definitely dries out. Didn't work as casting material ... too thin and flimsy. : )
-- b
Offline
Beth, see my next post, "Homemade casting rubber". You would never believe what the weird mix of the ingredients will produce!
Sue
Offline