A day in which I play Junior Scientist

Shortly after I met my husband, we both were given one of those Myers-Briggs personality tests. My test came back saying that I preferred “feeling” to “thinking”. In fact, I topped out the score in that particular category. It is no surprise, then, that I was never particularly attracted to engineering.

So it must amuse my husband that I now routinely come to him (a definite “thinker”) with engineering-type questions. I certainly have come to appreciate good problem-solving skills.

And that is what I needed for the problem with my inner pieces. I needed a way to seal the surface, and only the surface. I had already wondered if it might be better to spray some kind of sealant on them – something that dried almost immediately upon contact. My husband’s suggestion was that I find something with a wax base, since that not only would sit on the surface but could probably be removed with rubbing alcohol. He thought perhaps furniture wax might do the trick.

I decided to set up a test to see what might waterproof my plaster without soaking it through.

I didn’t want to wait for plaster to dry, so I used the backing off one of the bad Vixen rubbers. (I should note that here is where I made my first miscalculation. Well, make that plural. Did I mention that this post could also be entitled “How Lesli wasted a perfectly good day in the studio”? Anyway, the plaster should have been damp, not dry, because that’s how the plaster is when the mold is being made.)

All I had to do was sand off the keys and make it 1/4″ thick. As this picture shows, I made a rather big mess. But I got my thin slab of plaster to test.

Interestingly enough, thin plaster is surprisingly sturdy. It took several smacks with a metal hammer to get my test pieces.

And here are my candidate sealers; ScotchGard, furniture polish, matte varnish, dullcote, and wax resist. Off to the right is my control piece with my usual mold soap. I’ve etched a letter into the plaster chips so I know what’s what.

At this point, all I wanted to know was which of these actually sealed the plaster. As it turned out, plaster is really hard to seal. ScotchGard doesn’t seal it at all, no matter how much is applied. Surprisingly, neither did the DullCote, though the varnish did. Unfortunately the spray was strong enough that I suspected I’d never be able to use an insert to protect the design area from the spray. The only two “alternate” sealants that worked were the furniture polish and the wax resist. Of those two, the wax resist was both more effective and easier to apply, since it brushed on just like the mold soap.

Like I said, this is how I wasted a day in the studio. It probably wasn’t necessary, although it was certainly interesting. After calling Joan to discuss my results, it became clear that my real problem wasn’t that I was using mold soap, but that I was following the mold soap directions. (I tend to do this, much to my husband’s frustration.) The instructions called for 8 parts water to 1 part soap. So yes, Sarah, my soap was simply too wet.

I still plan to make a comparison test. I want to seal one Imp mold with my soap (straight, no water), one with wax resist, and one with Joan’s soap. I am pretty sure all three will work, but I want to know which one works better. And next time I’ll just wait for the time difference (Joan is on the other coast), and use my “phone a friend” option!

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3 Responses to A day in which I play Junior Scientist

  1. Sans Souci Studios January 27, 2009 at 8:03 pm #

    Have you tried shellac? This is a traditional sealant for plaster maskmaking molds, which also need to be able to draw water from the cast. Just a thought!

  2. mel January 28, 2009 at 1:17 am #

    I’m not surprised dullcote doesn’t work—does it actually work for anything?!

  3. Joanie January 29, 2009 at 1:25 am #

    Plaster (wet plaster) sticks to shellac… at least, when we shellaced the brown clay of Orson, then poured plaster, I had to chisel the brown clay and shellac out of the plaster! Yikes! And plaster doesn’t stick to brown clay, so it was the shellac that was the issue.

    Wet plaster is very tenacious!

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