Extremely registered user
Join Date: Jul 2006
First, some definitions/explainations:
Gorilla Glue is a 1-part polyurethane resin. It cures by drawing in moisture from its surroundings.
Titebond is a brand name for a line of adhesives. In my experience, they are best known for their wood glues, a form of PVA glue.
Sawdust is a cellulose based filler. The most common form you will see it used is when mixed with air-dry adhesives to create "wood putty"
By "resin", I presume you mean polyester resin, sometimes referred to as "fiberglass resin".
By "Smooth-on plastic" I presume you mean 2-part polyurethane casting resin.
Any time you talk about combining multiple materials, such as glue+sawdust, resin+fiberglass cloth, or cement + steel rebar, you are talking about the wonderful world of Composite Materials.
The problem with using Gorilla Glue for any sort of casting or laminating purpose is that the mixture of the polyurethane and water (either applied, or sucked out of the air) causes the resin to foam up. When you use it as an adhesive, you clamp the two pieces together with enough force that the joining surfaces prevent the adhesive from expanding (visibly). The only foaming you see is what manages to squirt out the edges.
The ring project only worked because the guy sealed it into a mold that got clamped off on all edges. And after that, he cut the cast piece out and trimmed it down on a lathe. If you can't clamp your mold shut with a strong air-tight seal, the resin will foam up and give you a foamy bubbly surface, instead of the desired smooth surface. Even if you can clamp it shut, if you use a bare plaster mold, the glue would stick tightly to the plaster, forcing you to completely destroy the mold in order to extract the finished piece.
You can build nearly the same ring using a combination of sawdust and 2-part epoxy adhesive (no water) and you wouldn't need to clamp the mold tight; even an open-faced mold would work, since epoxy doesn't expand as it cures.
I'm afraid you're not going to find any DIY recipes for modern categories of resins. If there were, it wouldn't have taken us until the 20th century to figure out plastics like bakelite. In a lab scenario, yes, you can make a couple plastics, like nylon, or nitrocellulose. But the processes are either too dangerous or too expensive to be worth the effort.
I'm pretty sure that isn't really what you're asking for though. I believe you want materials that have similar properties to these resins, but with easier availability and lower cost.
You can make perfectly good composites using more easily obtainable, and cheaper materials. Paper mache is a fine example of this. Done properly, and starting with heavy-weight paper, you can make surprisingly strong props. And if you take the time to properly sand and surface them, followed by a good paintjob, you can make them indistinguishable from a well made fiberglass prop.
For more strength than the above combination of paper+paste, you can move up to a combination of white glue (PVA glue) and fabric. Inexpensive muslin fabric is generally sufficient, but for added strength, you can go as far as heavy canvas. The technique is pretty much the same: saturate the fabric with glue (possibly with some water added so it absorbs better) apply it to the surface, squeedgie off the excess. Apply successive layers while the previous layer is still slightly wet.
You can combine plaster with a number of synthetic-rubber type products to improve it's strength and durability. Industrially, this is done with an acrylic-based product. I most often hear of a brand-name product called "acryl-60". But elmer's glue, mod podge, or even latex housepaint used in place of some of the water can increase it's strength.
That said, I don't like casting plaster for props; they are just too heavy.
Another thing is that the "liquid plastics" (2-part polyurethanes) work REALLY well for casting. You stir it up, pour it in the mold, and it clicks over in a matter of minutes. You can reduce the weight and increase the strength by adding things like microballoons or walnut shell. And once cast, it sands, carves, and paints really well. Once I tried it the first time, I didn't really want to be bothered with much anything else.
Hope this helps!