Heat Drops fast!

[dimitrisbizakis]

Re: Heat Drops fast!

Hot on the outside and temp dropping fast sound to me like the oven is still wet. The remedy is to keep firing. My bet is that if you do this a few more times you will find that the outside is barely warm, the temp rise much faster and heat retention much better. But be careful and take it slow. Forget pizza for a while and just roast and bake until it's really dry.

I will take your advice and start with baking small batches of bread!
I just need to make a good oven door now...

[dimitrisbizakis]

Re: Heat Drops fast!

30 cm! That sounds like a lot. If it is all a perlite/cement mix then you have added a ton of water. Do a calculation of how much perlite you used in total and divide that by 3. That will be about how much water you have added. It takes ages for this mix to dry. See attached doc. Slow fires are the only remedy and as you have already rendered over it, the moisture will not be easily driven off. Remember that one litre of water will make 1600 litres of steam. That's the big advantage of using blanket, rather than perlcrete or vermicrete, it doesn't contain water that has to be removed.
Good Luck.

The first layer of perlite (15cm) has been set from the an old cob oven, over that layer has been poured 15cm additional so the moister i think is from there.
I haven't render the final layer of the dome yet because if there is a insulation failure i want to have the choice to remove the Ceramic Blanker an fix the problem.

[david s]

Re: Heat Drops fast!

30 cm! That sounds like a lot. If it is all a perlite/cement mix then you have added a ton of water. Do a calculation of how much perlite you used in total and divide that by 3. That will be about how much water you have added. It takes ages for this mix to dry. See attached doc. Slow fires are the only remedy and as you have already rendered over it, the moisture will not be easily driven off. Remember that one litre of water will make 1600 litres of steam. That's the big advantage of using blanket, rather than perlcrete or vermicrete, it doesn't contain water that has to be removed.
Good Luck.

[dimitrisbizakis]

Re: Heat Drops fast!

Its 2 layers of 20cm and 10cm of 10:1 perlite mix.

[brickie in oz]

Re: Heat Drops fast!

What insulation have you got underneath?

[david s]

Re: Heat Drops fast!

Hot on the outside and temp dropping fast sound to me like the oven is still wet. The remedy is to keep firing. My bet is that if you do this a few more times you will find that the outside is barely warm, the temp rise much faster and heat retention much better. But be careful and take it slow. Forget pizza for a while and just roast and bake until it's really dry.

[dimitrisbizakis]

Hi everyone,
I think maybe this is a curing issue but this is how it goes.
I have one layer of 25mm on the side of the oven and two on the top an just a layer of perlite for leveling of steping gap between the two layers.
After the second fire the temp's reach 300c and the dome is white, two hours late with the door closed and empers inside the dome the temp is 150c!!!!
The external of the dome is just hot to the touch, i thing about 40c.
Just for the info, the dome is ready for the past month now so it's prety dry...i think.
Hope i didn't make something wrong.

Thank you all in advanced.