All experienced amateur vacuum people know the virtues of Hysol 1C Epoxi-Patch for fixing leaks, turning bad interconnects into OK ones, assembling stalk shrouds, and making DIY feedthroughs.
I had read about a procedure for making your own "epoxy clay" and it occurred to me to try it with Epoxi-Patch. The procedure I had seen involved mixing epoxy resin with Plaster of Paris as a thickener. I instead used a powder which is apparently rather like what Plaster of Paris would be if it were somewhat less brittle, made of zircon-magnesia, and capable of surviving a temperature of 2800 F.
(I am worried about hydroscopicity. Probably a better material would be magnesia powder or fumed silica. Guess what I don't have on hand? I intend to dampen and then dry them before use.)
My test pieces are curing. If this works, it may provide an economical alternative to glass blobs and 3D-printed Ultem.
High Vacuum Modelling Clay
Re: High Vacuum Modelling Clay
Have not yet tested in vacuum. This has been under construction for a very long time. Assuming it works, the only part remaining for my next experiments will be a KF40 tee.