Since we're talking about different plasters, here's a bit about Excalibur. I got my 50 lb box in the mail and it was HEAVY (hmm... about 50 lbs I'd guess) but a lot smaller than I'd thought. Here's the box:
Just to give you a sense of scale, the box is 12"x12" and 11" high.
Inside is a big ole' bag of powder:
And, for the curious, here's the instructions on the front of the box:
That's what I call a User's Manual!
Compared to Permastone, this stuff sets fast... REALLY fast! It's not kidding when it says 12-15 minutes to set! You need to scrape pretty quickly after pouring, and then you can seriously pull the parts out of the molds in a little less than 20 minutes! With the Permastone I'd wait a good 40 minutes before pulling the pieces out of the molds.
I used the Wet Water method on pretty much every mold I cast, and it seems like the Excalibur is a little more forgiving and produces fewer bubbles than the Permastone.
People told me that Excalibur was a lot stronger and heavier than Permastone, but I didn't notice that much of a difference (I haven't broken any of either material yet). When I weighed them, the Excalibur pieces are about 1.2 times the weight of the same Permastone pieces.
Now,
a few posts up, I posted a table that indicated that Excalibur would be the cheapest per
pound. Now that I've used the Excalibur, I'd guess that Durham's will probably end up being cheaper per
brick because Excalibur is so dense (the water can soak up a TON of this stuff!). I'll reserve my final judgement until I try out the Durham's though.
All in all, I like the stuff. The bag-in-a-box packaging isn't the greatest (I prefer the tubes that the Permastone and Durham's come in), it's expensive, and you can't just run to the store when you need some. However, the casts I've made with it seem pretty good!