Last week I finished my 100lb bag of UltraCal 30. Based on the feedback from some other users of this forum I picked up a bag of Hydrostone from Larsen Foundry
Supply.
Since I was trying a new product, I decided to look up the mix ratios online. The datasheets I saw suggested mixing 32g water to 100g plaster. This yields enough to slightly overfill a deep mold (like the basic brick mold) or about 1.5 of a floor tile mold / accessory mold. The result was very much like a milkshake, but the last 20-30g of plaster were somewhat difficult to mix in. I ended up with a few bubbles (this mix is far too thick for the cavern accessories mold imo), but am very impressed with the Hydrostone as a plaster. A few things of note:
Shrinking: When I was casting in UltraCal 30, the 3" long brick from the basic mold always came out 1/16" short. With Hydrostone, even after fully drying my caliper shows it almost dead on. (I have seen up to 1/128" off in either direction. Really, I don't see any shrinking from the hydrostone.
Casting Time: For the past two years, my tendancy has been to do only 1 casting per sitting due to the amount of time it takes for UltraCal to de-mold. (about 50 minutes). With Hydrostone, this has changed dramatically. On Saturday my wife took the kids out of the house and I decided to see how much I could cast while she was out. I poured my first mix (double the above values), poured into the mold and started my second mix. By the time I poured that mold, the first was ready to scrape. I poured the second, mixed the third. As I scraped the second molds, I looked at the first batch and realized they were already ready to de-mold. I < 2 hours I was able to cast each of the molds 3 times.
All in all, for about $2 more a bag I'm able to get three to four times the number of casts. I'll need to play with the water ratio a bit more to work out the bubble (or start using my massager on the table again), but I'm very pleased with the new plaster and thought I would share those thoughts.
Now that I'm able to cast at a decent rate, I'm actually going to start some of the larger projects I've been considering. Hopefully I'll have some images worth posting soon,
Dave
Since I was trying a new product, I decided to look up the mix ratios online. The datasheets I saw suggested mixing 32g water to 100g plaster. This yields enough to slightly overfill a deep mold (like the basic brick mold) or about 1.5 of a floor tile mold / accessory mold. The result was very much like a milkshake, but the last 20-30g of plaster were somewhat difficult to mix in. I ended up with a few bubbles (this mix is far too thick for the cavern accessories mold imo), but am very impressed with the Hydrostone as a plaster. A few things of note:
Shrinking: When I was casting in UltraCal 30, the 3" long brick from the basic mold always came out 1/16" short. With Hydrostone, even after fully drying my caliper shows it almost dead on. (I have seen up to 1/128" off in either direction. Really, I don't see any shrinking from the hydrostone.
Casting Time: For the past two years, my tendancy has been to do only 1 casting per sitting due to the amount of time it takes for UltraCal to de-mold. (about 50 minutes). With Hydrostone, this has changed dramatically. On Saturday my wife took the kids out of the house and I decided to see how much I could cast while she was out. I poured my first mix (double the above values), poured into the mold and started my second mix. By the time I poured that mold, the first was ready to scrape. I poured the second, mixed the third. As I scraped the second molds, I looked at the first batch and realized they were already ready to de-mold. I < 2 hours I was able to cast each of the molds 3 times.
All in all, for about $2 more a bag I'm able to get three to four times the number of casts. I'll need to play with the water ratio a bit more to work out the bubble (or start using my massager on the table again), but I'm very pleased with the new plaster and thought I would share those thoughts.
Now that I'm able to cast at a decent rate, I'm actually going to start some of the larger projects I've been considering. Hopefully I'll have some images worth posting soon,
Dave
