Well, poured the Ultrasil for the Tower builder mold last night and it set overnight. Fresh Ultrasil only takes about 4-6 hours to completely set. Brushed the Ultrasil onto the master to reduce bubbles in the undercuts. Gives you a nice close and clean mold but I had to destroy the master to get the mold off it fit so well. I was also a lot more generous around the walls of the mold as I’ve noticed the wall builder mold occasionally deforms when casting. Poured the first tower builder cast before I left for work this morning and it’s setting now.
Also filed down some cast walls last night and dry fitted them for a tower base. They go together ok although I notice there’s some subtle ‘bowing’ in the casts. Probably because the wall builder mold is quite thin on the bottom.
I’ve noticed that Ultracal 30 has a considerably longer de-molding time than Hydrostone. Hydrostone casts could usually be de-molded in about 15-20 minutes. Ultracal casts are best left an hour before demolding. Ultracal is also a greyer stone once set – although I’m painting over all my bricks of course.
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