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I'm doing sculpture and I've been playing around with some microcrystalline wax. The pliability of it once warm is great, but I'm running into the problem of it tearing / ripping when I stretch it. The same issue causes problems when smoothing it out, as the surface "gives way" under my finger if I press hard enough.

I've tried mixing in petrolatum and mineral oil in various different quantities but with no success; both just make the wax stickier and softer with no elasticity benefits. Is there another method which will increase the stretchiness?

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The wax (presumably a mixture of mostly n-alkanes?) constantly re-crystallises under strain, making it brittle in the same direction. Petroleum acts as a plasticiser, easing the flow of the amorphous phase, but also easing the recrystallisation even more. In effect it doesn't really help with your problem.

You could try to find another, harder wax with longer alkyl chains, and try softening that by mixing in your present material.

And generally take your time when working it. When the material becomes less opaque, i.e. whiter, then it is already hardening. Stay below that threshold. High strain rates let the crystallites grow, which are stiff, so at the edges of the crystallites, the strain rates are even higher.

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  • $\begingroup$ Natural bee wax is most certainly not a mixture of n-alkanes. Other than that, you are mostly right. $\endgroup$ Commented Oct 23, 2016 at 16:02
  • $\begingroup$ I was thinking the OP meant paraffin. Beeswax is rather not microcrystalline, is it? $\endgroup$
    – Karl
    Commented Oct 23, 2016 at 17:16
  • $\begingroup$ @IvanNeretin Why "mostly"? ;-) $\endgroup$
    – Karl
    Commented Oct 23, 2016 at 17:27
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I use microcrystalline wax all the time but mine is now soft and tacky and very bendable when I pour sheet wax. However, with you issue, it is best not to BEND the wax while it is still warm, even though this is tempting, it will break and tear. It is best once you have your form or sheet, to leave the wax go completely cold before attempting to twist it or bend it.. works well and better.. don't try bending or manipulating when it's just completed it's cooling process.. I'd pour a few waxes and leave them for a day until they are well cured and cold.

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