Tag Archives | Pour Horse

Fixing the leak (mostly)

Thanks to the now-working mold straps and some tips from fellow ceramists, my Elsie mold has gone from extremely leaky (bottom) to a more normal amount of flashing (top). I had underestimated just how much I needed to thicken the slip when working with a much larger casting.

I also discovered that I got much better results by pouring successive castings. Because I live in a pretty humid climate, my molds have to sit for considerably longer before I remove a casting. Not wanting to wear my molds out – which getting them too damp too often will do – I had been spacing my castings out over a period of days. My typical routine was to pour one casting and then let the mold sit for one or two days, then casting another. Joan at Pour Horse had suggested doing two castings in a row and then resting the mold. That is working much better.

Now if I could just find enough uninterrupted time to glaze a set. As much as I would like to have a set finished before the end of the year, scheduling tends to conspire against me during the holidays when it comes to things like underglazing. I can do a lot of tasks (like art glaze giftware or clean greenware) in small bits of time with lots of interruptions, but not underglazing. The threat of being interrupted – which seems worse that usual during this time of year – is enough to make me avoid the spray booth. Perhaps I should ask for a day of isolation for Christmas!

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Learning from mistakes

I tend to focus a lot on mold-making on the blog, probably because it is the area of my work where I still have so much to learn. Blogging is a lot like talking, and like most extroverts I process my thoughts best outside my own head. It has made for a messy conversation, at least for anyone else wanting to learn mold-making by reading, because it seems many of my posts are about what I should not have done.

I have been blessed throughout my adventures in ceramics with an extremely generous and patient mentor. Joan has always been available to answer any questions I have had, and to offer whatever help she could. But she does live 2,400 miles away. That means she cannot look in horror at something I am about to do, and cry out, “Oh no! Don’t do that!”

Which is a big limitation when I assume I understand the next steps. I am usually a pretty decent problem-solver, but sometimes I just miss the obvious.

For some reason, when I made the second version of the Vixen master, I had it my head that I needed to end up with two separate, complete masters for the two different molds. I was used to thinking of master molds as exact – or at least almost exact – copies of the plaster molds they made. I knew the first master, which cast a whole Vixen, would need to hold the different rubber pieces (her head, her one front leg) so that separate molds could be made of those. What I didn’t realize is that I didn’t have to destroy that original master to do it.

I didn’t need perfect masters of the eventual production molds. All I needed to do was temporarily modify the master to make the separate molds. If I could do it once, I could do it again when another production mold was needed. And if it didn’t work, I could always modify it a different way the next time. (That is what I cannot do with the current Vixen master mold, now that I am unhappy with the modified design. Darn!)

This is what I should have done. I’ve boxed up the (unharmed!) Elsie master and just blocked off the area that will make up the separate mold for the head.

The mold sides are rough since I didn’t bother to smooth the clay barrier, but a planing tool can fix that easily enough. That way this piece, and the one already poured (visible in the previous picture) and the rubber head can all be boxed and the final piece poured.

I did find that because of the angles of the cut to her neck, it was better to cast the other side of her face second since it gave me more control over the angle the plaster made with the opening of her neck. When this particular mold was finished, the edge was thin enough that I suspected it would crack before too many pieces were cast.

What I didn’t remember was that when I poured the plaster for the first piece, I had inserted both the rubber head and the rubber body because there is a small gap where that inner piece meets up with the body. I didn’t include the body the second time, so of course some of the plaster poured down the gap and into the body cavity, where it pooled in the tail.

Now I have two Elsie head molds and a white plaster Elsie butt. Next up – the body! I am sure it will be a learning process as well, and I’ll share any of the mistakes here.

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