Hello,

I am very new to this forum, but would like some advice.  I am a ceramic maker in Edinburgh and have started to develop work that is made using something called a jigger jolly machine.  It is a difficult process to describe but it is a hybrid between throwing pottery on the potters wheel, and turning it on an engineering lathe. A plaster mould is placed on a rotating cup, clay is introduced, and a template arm comes down and presses the clay against the plaster.  The plaster removes the water content enough so the work can be removed.

an example of my jigger jolly machine making a cup:


I apologise in advance for the specific vocabulary.  I know that toolmakers and model makers will have different terminology, but I think they are pretty similar processes to mine.

I am trying to economise the process of mould making.  I have been going through the traditional process of making a plaster model, placing it on a filled in back, putting the ring on top, and pouring plaster in to make a working mould.  The pictures below hopefully illustrate what I have been doing:




What I've done is to cast into this working mould with Easy Composites CS25 RTV silicone to produce a tool that keys into the metal back.  I then fill in the remainder of the back to stiffen the silicone and to keep it in place and make working moulds off of them.


I guess what I'm asking is am I doing this the most efficiently? I have scaled up the tooling to be able to make much larger things, but If I use this silicone method, It will become very expensive.  Should I use some kind of core material to use less silicone?
Any help or advice would be greatly appreciated.

Thanks for your time, and please get in touch if you have any questions.

All the best, and keep on making,

Chris Donnelly

Very interesting process and nice end result. 

To limit the use of silicone , you can build a former for the reverse that fills a lot of the dead space that would normally fill with silicone.  You can use wood or foam or even polystyrene cut to shape.  Suspend it above the void leaving a 1-2cm gap to be filled with silicone.  Then do your pour.  Once cured you can either remove the former or leave it in place for support. If the material you used is not porous, then you can remove and refit at will so you can refit it to support the silicone during casting, then remove to help flex the silicone for demoulding.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant