RMH finish - what to use for render!

Hi all

So we've built an excellent heater based on Matt Walker's batch design and so far it's working really well.

Just wondering if anyone has any recommends for a top coat plaster. We've rendered it with the same 3:1 (kiln dried sand : fireclay) mix we used for the mortar, but the art department would like it smoother! We've not had great results mixing fireclay with soft (builders) sand (lack of adhesion) and I'm wondering what to use.

Our nearest pottery supplies store here in the UK sells plaster for making pottery moulds.. guessing that should work, or maybe there's an easier solution?
https://www.bathpotters.co.uk/potters-plaster-potp/p2290

Thanks loads!
Pete

Pete Johnson wrote:Hi all

So we've built an excellent heater based on Matt Walker's batch design and so far it's working really well.

Just wondering if anyone has any recommends for a top coat plaster. We've rendered it with the same 3:1 (kiln dried sand : fireclay) mix we used for the mortar, but the art department would like it smoother! We've not had great results mixing fireclay with soft (builders) sand (lack of adhesion) and I'm wondering what to use.

Our nearest pottery supplies store here in the UK sells plaster for making pottery moulds.. guessing that should work, or maybe there's an easier solution?
https://www.bathpotters.co.uk/potters-plaster-potp/p2290

Thanks loads!
Pete

Looks super nice Pete! Good job.

I’m not a pro at this, but I believe you want m-sand or some sort of stone dust for your finish plaster. If you want to add fiber cattail fluff can help to improve tensile strength without giving you too much lumps and bumps.

This video might give you some ideas and/or inspiration. He adds toilet paper to plaster and burnishes to get a really smooth finish. Also have a look at how fine his sand is.



In the end you’ll want to finish with a drying oil to avoid dusting for sure.

Hope this helps.

Good luck

✌🏽Peter to Peter✌🏽

You can use standard ‘Home Brew mix’ it is used for pizza ovens and can cope with 350c for long periods and even go as far as 500c for short periods  and is a delight to use!
One part lime, one part potters clay (fire clay), one part portland cement and three parts sand.

Thanks for the replies! I've been loving working with the clay (non-caustic, re-useable, etc) so I think I'll give the clay / sand / toilet paper mix a go..

Pete Johnson wrote:Thanks for the replies! I've been loving working with the clay (non-caustic, re-useable, etc) so I think I'll give the clay / sand / toilet paper mix a go..

Let me know how it works out for you. He does a pretty good job in the video illustrating the process. I’m keen to try some as well when I get the time.

Cheers, Pete!🏔🥷🏿🏔