Casting a Flexible Object

[Ben xyz]

Though I just completed a casting workshop (plaster mold with slip), I hit a brick wall in how to cast a flexible object such as a smaller inflatable toy. (7”x5”x4”)
1. I figure that first the object needs to be non flexible to proceed. Tried foam insulation through the inflatable’s nozzle, but it became a lumpy mess.  2. Thought of getting a 3D scan and rigid model produced, but the cost to do this appears to be quite high.   3. Using 12” wide plaster bandages over the object to make it rigid. Then apply a sealant and finally Vaseline to creat the  mold. This seems like it should work. Thoughts? Thanks!

[JohnnyK]

How about a photo of the toy. It might help with suggested solutions...

[Min]

@Ben xyz, like Brett Kern's dinosaurs?

 

[Ben xyz]

Thanks Min - interesting process. May have to make my own inflatable, as well. I think that making my own object rigid to start will help with possible plaster leakage. Plan to watch the video again and perhaps learn more. It will likely be trial and error experiments to get it right. Will check back in if all else fails. Appreciate the suggestions, guys!

[Min]

Is filling the toy with plaster an option? If so you could fill it with plaster then either cut and remove outer layer  or leave it in place if it is plastic to cast as a two part mold then cure and seal and soap up the plaster and cast that. Like Johnny said a picture would help with ideas.

@Jeff Longtin, have any ideas?

Edited October 18, 2022 by Min

[Jeff Longtin]

A couple thoughts: would it be possible to inflate the toy using water? Potentially you could freeze it , after its filled, to make it solid.

You mention foam insulation...have you tried the foam tire inflation kits that bicyclists use? I'm told they work really well to keep a tire inflated.

Another alternative could be latex rubber.  It would flex with the form but you could apply several layers to develop strength.  

An extreme thought would be to put the inflated form into a box and then fill the box with alginate.  Once set you would gently cut the alginate and remove the toy and then fill the alginate mold with plaster.

[Ben xyz]

Interesting considerations, Jeff. I like the frozen form, though the heat from the drying plaster might reek havoc. Will likely go with the 12”w plaster bandage sheets, then sealing with an oil-base gloss medium, before continuing with Vaseline and casting (using wet clay under it for support and seal for each of the two sides).