I continued to toil on the dungeon today, and slowly - oh, so slowly! - it continues to grow...
Ah, you've noticed the different shades of gray? No, I haven't started painting... I've begun experimenting with adding color to the plaster. My intention is not to replace painting the dungeon, but to minimize any "white chips" that could show if the plaster flakes. Here are today's four contestants:
Delta Ceramcoat Charcoal
This is what I used for most of the day, since it was handy (it's the color I plan to prime the dungeon with, so I've bought a few bottles of it). The experiment is simple: squirt some paint into the mixed plaster, then pour it into the molds as normal. And it works!
The blocks cast as normal, although I think they're a little softer. The color varies quite a bit, but then, I'm just eyeballing the amount. Even though I'm stirring thoroughly to mix the color in, some of the blocks are blotchy - and a few have a dark "clot" in the middle, I have no idea why.
Apple Barrel Black
I went to Home Depot (a home improvement store) to try and find "cement colorant powder" which someone recommended yesterday, but struck out. (The helpful staff member steered me towards the tile and grout display, but no colorant there...)
On the way back, I picked up the cheapest bottle of plain black paint I could find - Apple Barrel Black, $2.67 USD for 8 ounces at Wal-mart (exactly half the price of Delta Ceramcoat's Black in the same display). My thinking was that black would be more efficient at coloring the plaster than adding the Charcoal (a dark gray color), so maybe I could add less and still get a strong gray tone to the plaster.
I've tested two batches so far, and to my surprise, the mixed plaster has turned out unusually thick - like a premium milkshake. Now, these batches were also the first with a new box of "no name" plaster - but later batches of the same plaster have been fine. I need to test further, but I suspect that this paint is causing some reaction in the plaster.
Black India Ink
Not sure why I tried this, but I dumped some India Ink into one batch. The ink broke up when mixed into the plaster, until the plaster turned a very light gray color with lots of black spots in it. The spots disappeared as the plaster dried.
So, I still haven't found anything that India Ink is good for...
Liquid Concrete Colorant
Being persistent, I returned to Home Depot and this time located concrete colorant (in the "concrete" section). Well, they didn't have any powder, but they had bottles of Liquid Cement Color (black, brown, buff, and red) for just under $5.00 USD a bottle.
The instructions say to add this to the water, then add the concrete mix (or in our case, the plaster powder). The liquid color is jet black - I got some on my fingers opening the seal, and was afraid I'd just dyed my hand (no, it washes off with water). I didn't know how much to use, so I poured a small amount into the water, and ended up with a nice, medium gray plaster.
However... Liquid Concrete Color, while noted as compatible with concrete and mortar, is apparently incompatible with plaster. After an hour of waiting, the plaster was still liquid in the molds, and I threw it out.
More on the Two Plasters
I finished what was left of the 8-pound box of art plaster, ran through another 5-pound box of "no name" plaster, and just got into a third 5-pound box when my working time came to an end.
I think I understand what the tutorials at the Hirst Arts website say about mixing plaster - keep sprinkling it into the water until it won't absorb any more, then stir it up and pour it into the molds.
Well, what I'm observing is that the "art" plaster uses more water (and less plaster) to create a given quantity of mix. Which means the mix creates more blocks, but the mix is runny and the blocks are softer. Also, this brand tends to have small lumps in it, and is more difficult to scrape (it's either too watery, or it's too late and bits of hard plaster are getting knocked around when you try to scrape).
Meanwhile, the "no name" plaster makes a much denser plaster mix, using the identical mixing process (it uses less water and more powder for the same quantity). Lumps are less of a problem. It can be scraped fairly quickly, and is usually not watery (so it's easy to scrape accurately).
So... I wonder, if I had any more of the "art" plaster, could I try to force more powder into the mix to make a thicker plaster mix? Or, since the water is already at saturation point, would that even work?
I recalled reading someone saying that it wasn't necessary to wait until the blocks were completely dry before assembling them, so I dabbled with that today. I even tried gluing a few blocks directly out of the molds. It all worked. However, one of the three-block pieces snapped in two on me - but right along the block-seam, so it was no problem...
Status Report
I'm casting six molds at a run - it would be five, but six is a convenient number as I know how much mix I need for groups of three molds. I'm using two regular gothic floor molds, two gothic dungeon (block) molds, and a large gothic floor mold (for the extra-large tiles I'm using for rooms) - plus whatever mold is handy as the sixth mold (I figure I'll use the bits on some other project...).
My floors are coming along faster than my walls, so right now I wish I'd ordered a third wall-builder mold! I'm nearly to the halfway point with floors, but walls are taking longer to cast up.
Also, my dog stepped on one of the modules and broke it along the glue line, so maybe I should reconsider putting some kind of support on the bottom of these pieces. On the other hand, the damage was easy to repair with a little glue...