The 2 gallons of Vytaflex came today so I mixed it up and filled th 294 mold with it, the 2 gallons wasn’t quite anough to completely fill the mold, but as long as all the detail is covered it won’t matter as I have to add a 3-1/2″ deep plaster backer to the rubber when it’s cured anyway. Now it will need to sit and cure overnight before it can be removed from the mold.
The rubber positive with it’s new plaster backing block is out of the mold, now the keystone is approximately the same depth the original 1895 sculpture was before I made a shallow mold of her way back around 1980 to eliminate the back that was normally embedded into the brick wall, so the casts could hang ON the wall.
But now with wanting to make her in terracotta she will need the full depth.
I have some final patching and texturing of the plaster to do yet, but I expect I‘ll be working on the plaster piece mold of her this weekend.
The rubber cast is so I can take a plaster mold off this and not have any concernes about it getting locked together by slight undercuts and opposing surface angles, the soft rubber will “give” and the plaster doesn’t adhere to it
The first plaster piece mold section is made for the 294 keystone after I applied a layer of clay to the plaster backer block so I could square the side up and give it some texture. The clay used that way works nicely since the plaster block is still wet so it won’t absorb much water out of the thin layer of applied clay before I poured plaster over it. Now that the plaster section is hard that thin clay under it is no longer needed and it will be scraped off when the plaster mold is done.
3 more sides to do the same treatment with and then a few more sections for the face and base to be done yet too.
I might go and make blocks molds off these plaster pieces so I can make more molds as needed as easily as pouring the plaster rather than having to set up and mold all these sections one by one like I am here.
The block molds would be individual rubber molds of each plaster section, taken off them before this plaster mold gets any wear or damage.
Supposedly plaster molds wear down fairly quickly from the highly abrasive course terracotta being pressed and rammed into them, but in the old days it was of little consequence as almost every building had custom made ornaments on them, so they might only have made 4 or 8 identical keystones for the building anyway- not hundreds of them. More common ornaments like cornices they would have used a lot of and on multiple buildings, so they had to constantly replace the molds of those as they wore out.