perlite

[gaetanin]

I have managed to get c400 grade perlite to mix with my cement for my ovens first insulation coat over the dome, does any one know if c400 is ok and if so do I use at a 6:1 ratio, or is it too fine. thanks Ugo

[david s]

Re: perlite

Sorry, I don't know what C400 is but the ratio for perlcrete over the dome is usually leaner than 5:1. The more cement you put in the brew, the less insulating it will be. I use 10:1 which is enough for it to be still workable.Some folk go even leaner. Also I find a half perlite half vermiculite makes up a more workable mix than either of them alone for some reason. For every 10 parts you will need about 3 parts water.It's thirsty stuff

[gaetanin]

Re: perlite

thanks for that, will give it a go and see how I get on. Would you advise just 1 coat or more I have a 100 ltr bag of it so have lots I can use.

[david s]

Re: perlite

thanks for that, will give it a go and see how I get on. Would you advise just 1 coat or more I have a 100 ltr bag of it so have lots I can use.

you don't say how big your oven is, or whether you are relying on perlite as your only insulation material. Are you using a CF blanket under the perlite too?
4/3 x pi x r x r x r = volume of a sphere. Work out outside volume and subtract inside volume then divide by two because it's a hemisphere. Also add 20% because perlite volume will be reduced on mixing with cement and water.I like to do the layer about an inch and a half thick, then let it dry for a week before adding the next layer and so on. This way you can eliminate the water more easily later.

[gaetanin]

Re: perlite

I am building a 36in interior dia oven and trying to keep within the forno bravo instructions as much as possible, that's not been as simple as you would think as some of the materials are difficult to come by and can also be quite expensive here in NZ so far I have spent way more than ever intented. Yes I will be using a blanket thank you for your help I will reassess my notes before I progress any further.