For a number of years I had been looking for a light weight epoxy putty, that would work basically like Magic Sculp or Apoxie Sculpt, but the cured material would be light in weight. Epoxy putties can be a great material for altering ventriloquist figure heads or puppet heads, but the problem has always been, the more putty you add to the head, the more it is going to weigh!
I always try to keep up with what is going on in the mold making and casting industry (I've been doing mold making and casting since the latter part of the 1960's), and so I came across a new product that looked promising. Its been so crazy busy here with making cast parts and finished figures for customers, I didn't even get around to ordering it for quite awhile, and then several weeks passed before I was able to try it out.
I was somewhat skeptical before trying it, as I have tried so many dozens and dozens of other new materials over the years, and some few turn out to work exactly like you hoped they would, but many others have been a big disappointment and end up getting tossed. So how did this one work? Very nicely! I was pleasantly surprised. It is made by Smooth-On and is their newer Free Form Air.....
Here's my review of Free Form Air: First of all, Free Form Air costs less than Magic Sculp or Apoxie Sculpt. It's like 2 quarts of material for $25, which will go a long ways. Apoxie Sculpt is $35 for about the same volume of material, and Magic Sculp is around $40 for about that much material (you get a little more I think as you get 5 lbs. for that amount). In any case, the Free From Air appears to be a good value.
Next, it is very easy to mix. Much easier than Magic Sculp or Apoxie Sculpt or any of the other epoxy putties I've tried for that matter. Those are a little bit of a workout to mix in comparison. It comes out of the container very easily and is light and almost fluffy. It almost feels like you are not holding anything at first. But it's consistency is such that it will mix and blend at a much faster rate than the other epoxy putties.
Cured Properties: One of the first things you will notice after it has cured, is that it is not a hard as the other epoxy putties (it is only Shore D 50). Magic Sculp is Shore D 80, and from what I can tell, Apoxie Sculpt is in about the same range (fairly hard when cured). As a comparison, Free Form Air is somewhat comparable to basswood as far as relative hardness/softness. At any rate it is softer than what you may have worked with before.
In My Opinion: Because it is light in weight, you can use much more putty to alter a figure's face (at least twice as much is my gut feeling) and not have the head be too heavy. On the flip side of the scale, I would say it is great for altering a face, but there is a caution regarding other uses. Example: Some like to make heads completely cast from an epoxy putty material. I even show that on my web site as a way to make a head. Here's the reason for the caution.....
When I test a casting material, I always test its breaking strength. I need to know if 'push comes to shove', at what point will this material break? I create test samples about 1/8" thick and then see how much force it takes to break the sample piece. It takes a pretty good force to break a piece of cured Magic Sculp or Apoxie Sculpt. In the tests that I did, Free Form Air has about 3/4 to 1/2 the strength to resist breakage as either on of those.
For this reason, I would not recommend making a cast head with it unless it was properly reinforced and/or cast pretty thick (probably around 3/8" minimum). So closer to the thickness of a basswood head (basswood may actually be more like 1/2" or so in places). Otherwise, I think the casting will be too fragile. However I haven't actually cast any full heads in it yet to verify what might be required. I'm just putting that caution out there based on my destructive testing so far.
In any case, I think it has the potential to be a great material for a light weight alternative to the other epoxy putties, and thought I would share my preliminary findings on this product. It could make it much easier and more feasible to make a custom of or semi-custom face over an existing head casting using this light weight material instead of the heavier epoxy putties you might normally use.
Tip: When you first mix the material it is pretty much too soft to work with in my opinion. Let it set up a little (approximately 30 minutes) before trying to sculpt with it. It will have more body and be easier to sculpt when it gets slightly firmer in consistency.
Well, I hope you find this review of Smooth-On's 'Free Form Air' of benefit. I will be testing it out further as time allows.