Epoxy Putty vs. Normal Epoxy- Are they the same thing????

Good Ideas, you have given us. We use here epoxi putty for almost anything, from pipe sealant, to model building, even for duplicating parts, in supermarkets or craft stores you can get putty in different consistencies, form paintable ones (using a brush), creamy ones (using spatula or knives), to ones you can knead, they can accept up to a 5% of good quality thinner, so you can have all the choices to meet your modeling needs. The last one you can make it with a smooth finish by wetting your fingers, if you do this, put some cream to prevent adherence to your hands or fingers (if will not spoil the putty), the putty will also cure (reticulate or what ever you call it), even under water, also temperature will hurry the setting time. I have used it to repair lamps and chandeliers, boat hulls (real fiber glass boats), sinks, bath tubs, radiators, water pipes, gas pipes (only in emergency), there are many brands in the market, so pick the one you may have near and experiment. j3gm@yahoo.com.ar

I can recommend Milliput as being the best two part putty - It comes in standard and superfine flavors and is available from Micro-Mark.

What's the best two part resin, one that cures hard and dry, i.e. can be filed/sanded and is not sticky?

Excellent. I've seen the two part syringe epoxies at the store before, and was wondering if they'd work as putty (which I've learned they won't). I'll be sure to keep an eye out for the putty. Thanks!

(Epoxy 101...)

that is cool fredrickson, thanks for sharing that info

The short answer is at the molecular level, they are similar if not the same. From a functional standpoint, no.

To elaborate, epoxies typically come in a a 2 part system which needs to be mixed together.

Part A is the actual epoxy, which is basically a molecule with 2-4 epoxide groups, which look something like:

C - C - (Rest of molecule)
\ /
O

Part B is the curing agent. Typically it is amine (nitrogen) based, though it can also be mercaptan (sulfur) based. There are multiple reactive sites on the curing agent molecules.

During the chemical reaction, one of the oxygen-carbon bonds opens up and reacts with the curing agent. Since there are multiple epoxide groups on each molecule and multiple reaction sites on each curing agent molecule, you end up with a sort of uber-molecule (we engineers call it "highly crosslinked").

So pretty much all epoxies have the same basic mechanism. But there are dozens of alterations that can be made. Each time you change your Part A or Part B, you get a product with different properties (i.e changing your curing agent from one with 7 active sites to one with 13 active sites). Furthermore, you can add stuff to the epoxy to thin it down or thicken it up.

When somebody mentions epoxy in the context of modeling, I tend to think of the 5-minute or 90-minute systems you buy from the store. Typically they come in a thing that's essentially 2 syringes molded together; you dispense, mix, and apply. It has a consistency similar to honey.

The putties are much thicker (like play-doh or silly putty), and are probably good for carving/molding (like zimmerit). It's been several years since I've tried using it, but would guess that it's a marginal adhesive at best because it doesn't wet out the surface that well.

Hope this helps.