Paper Mache: Starch Revisited

GREETINGS ALL FLESH-SUITED,

In the past three days, I have been experimenting (finally!) with corn starch, as a glue for paper mache strips. So far, I've learned a lot about very desirable properties of starch, yet it brought more questions, as the issues showed up as I worked.


(Updated: Conclusion: I won't use it for now. See below for details)

I am hoping some alumni of tradition, and current paper mache users will come out of the woordwork to help us understand what works and what doesn't, and why.
Anyone here willing to share their insight?

Thanks!

WHY MESS WITH A GOOD THING?

Yeah silly, why switch to something so complex, when white glue and water work so well already?

REASONS: Ecology-Health-Durability-Convenience-Independance-Economy

You may wonder why am I so interested (dare I say haunted?) in moving towards more natural materials? I have always felt a bit uncomfortable about using so many synthetic materials to create my work, when at the same time I strive to be more eco-friendly and healthy in my profesionnal and personal lives. Those synthetics are usually much more damaging to the environment, from the moment they are created(transport+by-products+fumes), delivered (transported again, packaging) to the end of their use cycle (transport, waste) PVA adhesives are very sensitive to temperature changes, becomin softer in heat, and brittle in cold (albeit temporarily, it's enough to cause major damages or utter destruction). Also, synthetics are usually more expensive than raw materials, and come from specific suppliers. I prefer to buy local, to not be absolutely dependant on a single product (versatility and substitution are a must) and use supplies that will be easily available all year-round. I enjoy making my own art supplies, from relatively raw basic ingredients. So, using starch, such a common, inexpensive food ingredient, makes a whole lot of sense! Plus, it's been used by countless people, for many many years. If it's good enough for The Bread and Puppet Theatre and Ronnie Burkett, it should be good for me!

CURRENT TESTS
Skull and Neutral masks casts fresh out of the mold, not yet smoothed)

Skull on the left was the second test, and has better definition than the neutral mask on the right. Difference: I used only one layer of paper towel strips (release-detail layer) on the skull.

Materials so far: paper towels, coffee filters, thin kraft paper, corn starch (and of course the negative plaster mold, and water)

My current test is making two full-face masks out of paper mache strips, using negative molds made of plaster. The release layer (also serves as the "splash coar for details) is a single layer of paper towels (made from recycled paper, quite thin, stays put and works wonderfully) and water. Second and third layer, applied immediately but carefully, are brown coffee filters and corn starch (liquid, not tacky).

Fourth layer is thin kraft paper (wetted and wrung out to make soft) and corn starch paste (same liquid consistency). For my future masks, wether I use starch or not, I'll only use coffee filters for the first detail coat, as I found the brown paper towel, when properly softened prior to application, stays put and does not lift.

PHOTO at start of post: Skull on the left was the second test, and has better definition than the neutral mask on the right. Difference: I used only one layer of paper towel strips (release-detail layer) on the skull.

STARCH MIXTURE

To keep things simple, I just used water and corn starch.

Some people use white glue in the mix, but I believe it would defeat my purpose.

Preparation: (please share your own tested-and-true recipes, what I find online is vague and speculation at best).

Option one: I added some corn starch to a small quantity of cold water. Mixed as much as possible. Added boiling water gradually while stirring, until mix was more watery than wanted. It thickened as it cooled. No lumps at all.

Option Two: same begginning with cold water, then add more, place all in a saucepan, and gently heat while whisking like crazy, to avoid lumps. I wasn't very successful with the lump- avoidance (too hot for too long, probably), but I only made one batch this way. It was still useable. I want to try that one again, because sometimes I want a very thick, tacky glue. The problem with this mix is that it gets thicker with time, constantly requiring more water to be added, and lumps are created that way.

CORN STARCH AS PAPER MACHE STRIP GLUE
PROS:
•Natural, non toxic, inexpensive
•smell is almost undetectable, and is quite pleasant anyways.
•easy to mix to various consistencies
•dries matte and has a uniform color (I'd like to use that as a finish some time)
•applies quickly
•slick, creates no lumps on hands or brush or paper (when paste is well mixed to start with)
•dries as fast as white glue (I use a fan at l;owest settings, overnight)
•penetrates paper immediately
•seems to create a stronger result (as long as it is dry), so that less paper layers are required for a good structural strength.

CONS
•re-wettable, meaning a new layer will re-soften a previously dried layer or two.

...Meaning a paper mache session should last until at least the first TWO layers of strong paper have been applied, otherwise warping and shrinkage happen.

...so a hollow piece, such as a puppet head or a mask, will sag until dry again.
...re-assembling a multiple-part cast will be difficult, as the edges will sag from
...the added moisture.

•there is a limit of layers one can safely apply at once without having automatic development of mold on the outside or from within (corn starch+trapped moisture=food for micro-organisms). Information gathered online in a few place reccomends limiting to three or four layers, but that information is vague, as papers vary greatly in thickness and absorption factors. I'm thinking that since I am using a plaster mould, lots of the moisture is absorbed by the plaster. Since my casts remain in the mold for no more than 24 hours (but usually more like 16), I don't see why I should panic.

•when using thin papers, previous strips can lift quite a bit when new ones are being added (to the hands or brush), because of the rewettable factor. Mostly problematic on the first layer after the "release & detail coat" of paper and water.

•Absolutely needs to be sealed VERY well. Otherwise, the paint job itself can make it soggy and warp it. Or later: accidental spills, atmospheric conditions (even indoors), will damage it in no time at all.

•Seems to shrink a bit more than the same object made using same paper but with white glue. But that might be false, as I haven't cast a copy of either masks in five years.


NOTE: the CONS are the same as when using Methyl Cellulose(also sold as Elmer's Art Paste) and its variant, Hydroxymethylcellulose. So solving it for starch might solve it for MC.

SEALING NATURALLY

I wonder what the Bread & puppet Theatre uses to seal/protect their giant puppets made with corn starch.

The logical continuation of my process is to keep using natural materials.

One of my current test masks needs to go to a customer fast, so I'll have to go back to my usual synthetic material (Weldbond) for the sealing and finishing. At least it is non toxic, and is a good primer for acrylic paint.

The other mask can be used to keep testing.

Shellac: Seems to be the best "natural" solution that I've seen so far.

I do have a local supplier for a water-based shellac, which is used for making "permanent" ink, but it feels too expensive considering the amount I will need to properly seal a mask. It works well on paper for drawings and painting, but on an object, it might be weaker than a traditionnal solvent-based shellac.

Wax: might soften my paper mache, will become sticky under hot conditions, scratches easily, and would attract dirt over time. I'd still like to test. Not a priority, unless new information claims to the contrary.

Linseed oil: Strong smell, might make project saggy, indecently long time to cure, risk of spontaneous combustion.

PAINTING:

If using shellac as a sealer...

• I don't know if acrylics will adhere to it (and oils take too long to dry). The logical process would have me use natural paints for this as well, but most bring their own problems, mostly of moisture and scratch resistance.

Watercolors? (nope, they would run when varnishing)

Egg tempera? (needs testing, and need a home-made varnish)

•I've tested it years ago, and I think using my own shellac-based paint (shellac+dry pigments+wood alcohol as a solvent), would ensure complete compatibility.

As with most paints I make, to ensure that the finish is no glossier than "satin", or to make it completely matte, I just add more pigment (oversaturate).

Still needs to be tested for scratch and impact resistance.

One problem remains: I usually reccomend a spray (and/or cloth) of rubbing alcohol to clean/disinfect the insides of my masks. Shellac fears alcohol, will turn white-ish. If anything runs or spills or sprays over to the outside surface of the mask, the finish will need repainting. Even if only the insides get ruined visually, it lowers the beauty and value of the mask.

NOTE: it is of the utmost importance to get a fresh shellac to work with.

Older than a year-old shellac may not set, ever, and remain sticky. Happened to me.

I solved it as best I could by using a wax paint over it. Itmasked the stickyness, and looked good. But the finish transfers to the hand over a half hour of hand heat (it's a wizard's staff prop).

Sadly, most shellac companies do not include an expiry date on their product.

You may still be able to get the date the store got the can, if you ask an employee of the store to scan it, and see in the system. I believe Zinsser was, a few years ago last time I checked, the only company that had an expiry date on the package.

When in a rush and willing to take a risk, I sometimes reach in the back of the shelf, to get the more recent product, if I know that store has good product rotation practices.

also, getting the less dusty container may be another clue that it is more recent.

Because most hardware stores don't dust every can every week.

One way to get away from that expiry risk altogether might be to get the shellac in crystal form, at a paint and pigment supplier. It's extra work (breaking, grinding, heating, mixing, bottling), that I'm not really willing or available to do, though.

Again, I would appreciate input and insight!
Emailing is better than posting comments.
Keep checking this post for updates and more pics.

THANK YOU!

Updates:

The casts were more trouble than I expected, and I felt I was running out of time to finish one of the masks, so I proceeded to complete both of them using my older, tried and true methods. Which brought more insight into the process.
My usual sealer (Weldbond+water) was not reacting ideally with the starched surface. The towel layer was seprating from the first strong paper layer, no matter how much I diluted my glue to penetrate through ad stick. So I had to rip out the paper towel release-detail layer, which I never have to do normally (it becomes part of the final smoothing). This time it created a texture that is a bonus for the skull mask, yet unwanted for the neutral mask. You can see both casts, yet untrimmed and unsmoothed, with a coat of matte paint (acrylic paint, touch of glue, with a bit of drywall compound), which is a good step to reveal surface definition and imperfections.

My current tendency would be to wait for further input from colleagues with experience using starch, as for now, after my tests, I see no further direction to take that would solve the problems that starch brings.
Remaining problems:
•re-wet-ability = warping = sagging = less definition and accuracy = casts hard to re-assemble seamlessly
•Appropriate sealer: requires testing, possibly Shellac.
•If shellac is used, then acrylic paint probably not appropriate. (shellac-based paint should work)

CONCLUSION:
Starch is not a viable option for me, for now.
I may change my mind in the future, but I have a feeling I will not experiment any further with this unless I get insightful information about the process. So far, no one has come forward.

At least, I don't see it viable for use to cast hollow shapes that do warp so much. White glue and water works very well, so that is what I am going back to. The starch would still work well for pieces that are only covered, and never hollowed out, but Methyl Cellulose works better for this, for my uses. One product of Methyl Cellulose: Elmer's Art Paste. But if you use a lot, some people recommend getting it from a chemical supplier (either as Methyl Cellulose, or Hydroxymethylcellulose).