Success!
Oh thank goodness - it worked! Above is the second press mold and it popped off easily with the tweaks. Seven more to go.
What a tease...the plaster looks like a block of Fluff!
Here's the ornament inside the mold box with freshly poured plaster (above). My mold boards are clear acrylic, which allows me to see what's happening inside. The boards are like a Chinese puzzle box until you get the hang of them, but this simple "L" design works great. I have this long version, but also a shorter version for small pieces. It's not technically necessary, but much handier.
The boards are placed alongside the edges of the backing tile and clamped into place. Then the seams, where they meet each other and where they meet the backing tile, are caulked with earthenware clay to prevent plaster from oozing out.
But placing the boards alongside the tile edge resulted in a mold a snidge too thin for my liking, even though I mixed three pounds of plaster. It'll work just fine, but I'll have to be careful. The forces involved with tile pressing are pretty strong thanks to Sir Squish, my tile press. This fantastic press works like a charm because he's geared, and so a modest pull on his lever results in a lot of force on the mold. So much so that I've unintentionally broken a couple of rather hefty molds!
But we want all that force because it ensures a good impression and a dense compaction of clay particles. This is my (silly) theory, and it is mine... ahem....AHEM...I think "shocking" the clay helps to dampen warp. I wonder if by smashing the particles through a slab roller (such as my Derby) helps to shock them into a new alignment, and then smashing them again in Sir Squish reinforces that alignment.
I suggest this for two reasons. First, I've noticed zero warp in my round ornaments, no matter how big they are, implying that a lack of the "suspension" span between any corners prevents a sort of "pull" those corners could exert - but it also implies something about the particles and how they were aligned in the process. And second, I noticed in the fire of the 2010 ornaments that only those pieces that lined the side of the convection vents between the broken shelves warped - all those away from those vents, in the middle, were perfect.
But we want all that force because it ensures a good impression and a dense compaction of clay particles. This is my (silly) theory, and it is mine... ahem....AHEM...I think "shocking" the clay helps to dampen warp. I wonder if by smashing the particles through a slab roller (such as my Derby) helps to shock them into a new alignment, and then smashing them again in Sir Squish reinforces that alignment.
I suggest this for two reasons. First, I've noticed zero warp in my round ornaments, no matter how big they are, implying that a lack of the "suspension" span between any corners prevents a sort of "pull" those corners could exert - but it also implies something about the particles and how they were aligned in the process. And second, I noticed in the fire of the 2010 ornaments that only those pieces that lined the side of the convection vents between the broken shelves warped - all those away from those vents, in the middle, were perfect.
Here you can see the clay caulking along the seams.
Anyway, what I decided to do to create a beefier mold for the next pour was to pop the boards up onto the backing tile. It's something I've been meaning to try, but I was a little worried about the boards sliding around.
Oops! A bit of a spill there on the right. I need to find a new mixing bowl for plaster. The one I'm using is rigid and large, so spillage is unavoidable. I need one strong enough for plaster's weight and the effects of mixing, but also flexible enough to squeeze in a spout when pouring. It has to be cheap, too, which is why thrift and dollar stores are great suppliers.
I was so happy to find this approach worked great, so I'll be doing this for the rest of the molds. I want a really thick block while also minimizing the use of plaster, and this piggy-back approach delivered.
We don't want to get thinner - we want to get fatter! Mission accomplished.
You can see the difference clearly in the image above. The thicker block on the right will let me press much harder.
You may be wondering why I'm making so many molds for an edition of one hundred, which when divided, allots about twelve castings per mold (excluding the ninth back-up one). Well, the first reason is that I want to be able to choose the best molds for production, those with the least amount of bubbles or other hiccups that require clean up later. The other reason is that for some inexplicable reason, some molds work better than others in terms of pulling, and I'd like options in this, too. Same methods used in making them, but oddly enough, each mold has its own personality and you don't learn it until you use it.
Mostly, however, it's because of the clay itself. Clay is abrasive while plaster is rather soft, even when cured. So every time I press clay into a mold, the clay abrades the plaster, progressively wearing down the fine details and edges of the cast. The moisture in the clay also compromises the mold, and after about six or eight castings, it can be too damp to use and must be set aside to dry again. I want each casting to be nice and crisp, so I'd rather pour a few more molds to ensure each collector gets a faithful piece. I also don't want to be slowed down in the casting process - when I get in a groove, I go. Creativity has its own inertia. So setting a wet mold aside and grabbing a fresh dry one keeps production humming along.
Technically, I should be able to get about twenty five to thirty pressings from a single mold. Ideally, I'd be using Hydro-Stone® instead of regular molding plaster because it's harder and would yield more castings, but its mixing process is still something I have to perfect. So for now I'll leave that for another day and groggier clay.
I'm really excited to see how the black porcelain turns out. Black is a rather unconventional color for Christmas, I know, but can you imagine how it'll look with its purple ribbon and the glow from tree lights?! Fitting for a Friesian I think!
"The painting leads the painter, and it becomes an intuitive experience." ~ Ardath Davis
