[Clayart] Parting Agent

[Snail Scott]

> On May 9, 2018, at 9:13 AM, Bill Karaffa <bkaraffa at centurytel.net> wrote:
> 
> I am casting some burner ports using Mizzou castable and was wondering about
> parting agents. Last time I cast them was long ago. I think I used either
> WD-40 or dish detergent…

You didn’t specify what you were using for the mold, but I’ll assume wood or brick. In any case, neither WD-40 nor detergent is a good parting agent for much of anything. WD-40 will do for very smooth, impervious surfaces that just need a little grease - cooking spray will work about the same or better, actually. Vaseline will do, but it’s icky to work with and tends to be streaky for applications requiring good surface quality (though that’s not really relevant here). For this, or anything with even a little porosity, I’d use soap. 

I like plain ol’ Murphy’s Oil Soap for most mold release purposes. I’ve used expensive purpose-made mold-release soaps, but Murphy’s does almost as well for a fraction of the price. For a not-too-refined application like castable refractory, it’s entirely sufficient. Plus, you can buy it locally almost anywhere, in the cleaning products aisle at Wal-Mart.  Apply one layer, let it dry, then apply another and let it dry, too, to build up a good coating. Buff if you like, though I doubt it’s worth the effort for burner ports!

Note that dish detergent is NOT soap. It’s a detergent - an entirely different chemical. So-called ‘soft soap’ and liquid hand soap are not actual soap, either: they are detergents, too. You gotta have an actual stearate for it to be useful as a mold release. Murphy’s is about the only actual liquid soap out there nowadays.

Snail Scott
claywork at flying-snail.com
www.snailscott.com