I just thought I’d post a quick follow-up to my previous post about using Jesmonite.
The other day, when we were cleaning out our studios prior to end of the year teardown, I discovered something I suspected but wan’t certain about Jesmonite— it is strong! I had a number of early attempts where the gel layer simply did not fill the mould properly, leaving voids, bubbles or thin spots in the first layer of the Jesmonite laminate. I had finished the lamination on these pieces, but when I pulled them from the mould, I discovered that they simply wouldn’t work for me. Some were disfigured, some were simply too thick, and some just didn’t work out the way I wanted. These were the ones I chalked up to experience (or lack thereof), since I’d never used Jesmonite (or any other fibreglass laminate) before and was trying to learn its ways.

Sidebar: You can make repairs by adding Jesmonite to itself. It sticks to a dry layer with no problems so you can patch pits and voids after you’ve removed the piece from the mould by mixing up a small batch of Jesmonite using less liquid so it becomes a putty, then troweling it into the spaces that need it. You may need to carve/sand it afterwards, which Jesmonite takes well to.The pieces I’d rejected simply required more work to repair than it would take to cast anew.
So anyway, getting back to my story, I had these unusable (to me), incomplete and disfigured castings that I needed to get rid of. In order to prevent some unknown artist from claiming my work as their own, I decided that prior to throwing them away, I would simply smash them in order to make them worthless to anyone else. I took a hammer and smashed one. Nothing happened. The piece flexed and came back without any noticeable damage, save maybe a chip or two.
It ended up that other artists in the studio were happy to give them homes, and I am confident that they are not going to use them in their own work without credit, which is the main reason I was trying to destroy them anyway.
All this time, I had been treating these pieces with the same care I would the plaster pieces they resembled, but they were incredibly strong. Who knew.
Now, I don’t recommend trying to smash your pieces, but when laminating Jesmonite to make a cast, be aware that with the fibreglass layers, it becomes much stronger than you might expect.
Final Verdict: Jesmonite is easy to use, safer than similar materials, cleans up with water and when laminated with fibreglass, produces an incredibly strong result.