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Saturday, January 5, 2013

Amaco Self Hardening Clay - Stonex & Marblex Review

I have been experimenting.  I thought I had settled on Creative Paperclay as the best I had found and was trying to do some figurines. Takes way too long for me. Creative Paperclay is too mushy for me, it's about the consistency of bread dough. After getting the basic shape, I can't get any more detail in the mush and have to let it dry and then carve and sand for detail. Takes too long. I have 3 sculptures unfinished because I'm just tired of working on them. Too much down time waiting for the stuff to dry, which is why I did three at once. I figured I would always have one to work on. Didn't work out.

I went back to the first clay I ever sculpted with, Amaco Terre Cotta clay. This is clay that needs to be fired for strength, I don't have a kiln. I don't care. It was so nice to just sculpt again. First thing I did was sculpt a bust of a woman, from my imagination. I was going to sculpt a smiling Viking woman with a helmet on. She started looking African so I went with that, then changed her features a little and she just looks like a determined woman. One day, a few hours, and I was done. Not completely done, some sanding and not sure about that base.

I went and got some more clay and tried to sculpt Audrey Hepburn. Maybe not quite right, but pretty darn close. (not dry in this pic)
This took a weekend and watching a few Audrey Hepburn movies. I went back to get some more clay at Michael's, but they were out. I looked around and noticed Amaco makes a couple of self-hardening clays. They are non-toxic and most importantly feel and work almost exactly like regular ol' clay. I bought a 5 lb box of Stonex and a 2 lb box of Artists' Self Hardening Clay. The latter was very hard. Not sure if it was supposed to be that way or just dried out.  It was probably on the shelf too long and dry. I added water to it and it soaked it up. It worked pretty well, though a bit lumpy due to adding water, some areas were softer than others. I can't find it anywhere. Even Amaco doesn't list it in their products, and I looked by product number. I think it's been discontinued and it had been sitting on Michael's shelf for who knows how long. If anyone knows, let me know.

The Stonex sculpture I did was a little too big for only 5 lbs of clay, or my armature (loosely wadded up newspaper so it can shrink with the sculpture as it dries) was a little small, most likely the latter. I tend to keep adding to fix things rather than reshape, keeping a watch on that. I ran out of Stonex and used LaDoll to finish her hair, thus the very white parts of her hair. Stonex is supposed to be white, and here you can compare to the whiteness of LaDoll (the very white) and the whiteness of Stonex.
I need to sand this down. As it dried, every little bump got bumpier. At first I found Stonex to work almost exactly like clay. The problem comes keeping it wet. I spray my sculptures with water from time to time so that they don't dry out. Stonex became very sticky, it was like working marshmallow creme. Still, it was the best self hardening clay I had come across.

I went back to Michaels and picked up a box of Marblex, their last box. I learned my lesson from spraying water on the sculpture and didn't spray very much. Marblex never got sticky like the Stonex did. It looks like about the same color as Stonex, though I haven't let this sculpture dry yet, still working on it. I also ran out of clay and used Amaco Artists' Modeling Clay, which is an air-dry clay. Very nice stuff but probably doesn't dry as hard as Stonex or Marblex.
This is supposed to be Angelina Jolie. I've tweaked her nose and eyes since I took this pic. Pretty darn close from the side, I'd say it looks like her. From the front . . . I still have work to do.Waiting for ordered clay to finish this, next week.

I ordered 50 lbs of Marblex from .  Good price. With the shipping, probably the same price I would get by ordering through Michael's. But I don't trust Michael's. They take forever to re-stock their shelves and I have found moldy (yes, mold that grows) clay there. And customer service is almost non-existent. I will say when I do talk to someone they are very nice and helpful, just rarely happens to catch someone who isn't trying to avoid customers.

Now that I've found a good self hardening clay which is durable and workable. I'm thinking I might set up a shop locally for portrait sculptures and whatever else my mind comes up with to sculpt. Sculpting a person right in front of me is a lot easier than sculpting from a few pictures. I don't need the person in front of me all the time either. Who wants to sit still for hours? Not me. See ya.


  1. Oh no. I just went and bought a couple of boxes of Marblex from Michael's until my order gets here. Sticky stuff. I guess I need to let it dry a bit before using. I'm disappointed, especially since I ordered so much of it.

  2. I have been looking for an air dry clay to work with and your blog came up when I searched for reviews of the Marblex product. I am wondering about cracking as it dries and if it really hardens enough to be durable.

    I will be watching for your updates. Thanks!

  3. Zanymuse, thanks for the question. At the time I wrote this I hadn't had any dry yet. The stonex sculpture has been drying for about 2 weeks, it's fairly thick. A couple of cracks developed around the neck. I should have kept a closer watch and looked out for those. I will moisten and patch. I do use newspaper as an armature, so that's probably the reason for the cracks. It couldn't quite shrink enough due to the paper. It didn't shrink a lot. Amaco's claim to durability and hardness look accurate to me. I would trust it enough to ship it, packed well of course, but it does feel and sound harder than regular clay.

    And on a side note, I got the 50 lbs I ordered today of the Marblex, beautiful, not sticky. But it has been in a cold truck for days, so I'll see if it gets sticky as it warms up. Hope not. More on this stuff soon.

  4. like the other comment, when i googled air dried clay, your blog came question is this...i want to make some small decorative bowls and perhaps vases and have no access to a kiln. what air dried clay would you recommend for such a project and could they be painted and "glazed" with a glossy coating (like skulpey glaze or something similar)? i like a rustic pottery feel ala rae dunn...and am leaning toward the stonex. thanks so much, i will check back for an answer...s

  5. Sharon, for decorative I would say stonex or marblex would work, they would definitely not be functional. They are very much just like clay and I'm finding they don't seem to actually be any harder, maybe a little, but still break if enough force is applied. I haven't been very scientific about it. I am trusting that they are harder since Amaco says they are self-hardening and not just air-dry. They can be painted, I haven't done that. Sculpey glaze I'm not familiar with. Next week I should be able to post some finished busts of Angelina Jolie, Clint Eastwood and Geronimo. I still like the stuff, best air dry clay I've found.

  6. This is an interesting discussion. I too am looking for the right materials, and have been reading up on the Amaco stuff. Not sure I know what the difference is between their Marblex and Stonex, other than one is gray and one is white. Have you been able to detect any other differences? I am looking to sculpt little animals & things in block form, so pretty think, probably 3x3x2' ish size, and hoping they wouldn't crack. Thanking you in advance for your answer...if you get this post. I see it was a 2013 discussion ;-)

    1. Stonex doesn't have little grains of sand in it. The only Stonex I used was really gooey, but I think it was just the batch I got. Shoulda just let it dry out a bit. You can probably get a better finish on Stonex by sanding it smooth when it's dry. The sand in Marblex prevents that. I asked them why it has sand in it, didn't really get an answer. The small size you want to do probably wouldn't crack, if it does, just wet it and fill in the crack and let it dry, repeat as necessary. I didn't have much problem with cracking.

    2. Great review, I appreciate you posting this! It was so helpful to me. I'm also making a jump from the real stuff to the air dry stuff and will definitely take your advice. Lovely sculptures. So glad you include some word on your techniques as well as purchasing advice.

  7. Oh, thank you for the reply! I couldn't find that info anywhere, and since I would have to order it, I didn't want to get the right thing. I definitely don't want the sandy version. Thanks :-)

  8. Thanks for posting about this! I'm also experimenting with the so-called artist's air dry modeling clay sold at Michael's and I wish I had researched more about it. I can't find this product anywhere except Michael's, as the other well-known online artist supply sites -- and Amaco itself -- only sell Marblex & Stonex. Like you, I wonder if that was a discontinued product that Michael's has kept in a warehouse, or if they re-package it just for Michael's. It feels like traditional clay and I haven't had any problems with it so far. I'm making some experimental pieces just to test it out, like a pinch pot, etc. My only concern is whether or not to try baking it. What have you found, after it dries, about the strength of the finished piece? There are no instructions for baking or firing.

  9. I dabbled in air dry clay in 2015 . My experience was not a pleasant one. Figurines I made cracked and broke easily after drying out. I didn't like the shrinking, either.
    I switched to polymer clay which is much better. It bakes in your oven at 275 degrees. Doesn't crack after hardening and is alot sturdier