Kastolite 19

[Extremedave]

I was sold on using this castable product as the insulation layer which I bought from a brick supplier in Minneapolis so I have 24 bags of the stuff but I am concerned about putting it down under the floor. Has anyone ever used it? I am in Canada and very poor access to the materials here and nobody knows what I am talking about.

[GianniFocaccia]

Re: Kastolite 19

It will work fine, IMO. According to the product description, it is rated to 1900F (overkill for home WFO application), has a superior cold crushing strength (gross compressive stress required to cause fracture) and the benefit of being able to be cast in odd shapes.

It appears to have the same R Value as IFB, so I would not cast it under the floor less than 6" deep, preferably 8". It is designed as a backup insulation, not hot face.

http://www.afsenergy.com/?wpfb_dl=621

[Cadott]

Re: Kastolite 19

I used kastolite 19 aka Kast O Lite 19 to make a 4" insulating layer underneath the hearth. I, too, bought it out of the twin cities. I poured it seven days ago and it still hasn't set up properly in my opinion. I can still put my thumb into it when I press it. The edges and the top are very crumbly. Its still damp to touch despite my efforts to speed up the drying with propane heat. I did not exceed the manufacturer's directions of 5.1 gallons per 25 lb bar. A 25 lb bag will give you one cubic foot of material.

[Cadott]

Re: Kastolite 19

I spoke with the sales representative today about the characteristics of Kast-O-Lite 19. He said the product set up 24 hours after it was mixed. The finished product will remain 'thumb print soft' on top and crumbly on the surfaces and edges. I was expecting something more solid but this will do. Before I go on, I will need to wrap metal around the pad perimeter to keep Kast-O-Lite from eroding away or compressing out when I start putting weight on it. I tried adding pictures. Lets see if they post.

[Extremedave]

Re: Kastolite 19

Ok, thanks for posting. I will be doing something similar... Using concrete to keep it in form... Will post pics when done.

[Extremedave]

Re: Kastolite 19

OK, I am ready to pour my Kastolite tonight but also bought some 1/2 inch ceramic board at a local supplier - only had 1/2 inch in stock - so I am thinking about going with 1/2 inch board on top of 4 inches of Kastolite but thinking that I should possibly go out and spend another $300 and go with 1 inch of board and 3 1/2 inches of Kastolite. Your thoughts?

[Cadott]

Re: Kastolite 19

Just finished putting the a 4" metal ring around the perimeter of Kast-o-lite pad. The ring should stop side crumbling and contain the compression of the dome wall after it is set.

I put my firebrick floor directly on the Kast o Lite 19. Everything stayed level--no problem. But then I discovered my pad was only 3 1/2 inches thick and I have one extra 25 lb bag of Kast o lite left. I will probably set the fire brick off and the put remaining insulated castable on on top. I will not be using any insulated board.

Good luck with your pour. One thing I came across after the fact; use warm water with your mix, about 70F. Also, consider the ambient temperature during the curing and dry out period. Warm weather is better. I personally found the dry out period for Kast o lite to take quite some time. Maybe your pad will be different, but I am still able to press a thumb slightly into the surface of the pad.

[SableSprings]

Re: Kastolite 19

If you don't have any ceramic board, use a little of the mixed Kastolite to put a thermal break between your hearth and landing bricks. Just pulling the six landing bricks out a 1/2" or so and filling the gap with some mixed Kastolite should do the trick.

[Cadott]

Re: Kastolite 19

The 48" interior diameter is now a 44" diameter thanks to the 10" abrasive masonry disk on the chop saw--dusty, but no problem. Going off-grid with cast iron components for the porch. It's design-as-you-go.

[Cadott]

Re: Kastolite 19

I am attempting to utilize an old cast iron Ben Franklin freestanding fireplace for the oven's porch. The fireplace has good angles on the sidewalls. I cut out the cast iron with an angle grinder. Once I start doing the dome roof, there'll be more iron cutting I'm sure. Now I wonder if I should pour cast refractory walls along the outside of the iron verticals or just go leave the iron stand alone. I removed the upper front plate and vertical side fronts for the time being.

[david s]

Re: Kastolite 19

However you do it just be aware that the cast iron is way more conductive than any refractory that you use. This means that it is likely to expand more than any refractory that surrounds it, which could cause fractures and joining difficulties between the two materials.

[Extremedave]

Re: Kastolite 19

Here is how I built a form for the Kastolite. It was a blank in concrete which I lined with foil leftover from my sauna build. I then poured the Kastolite and left about an inch and a quarter of space on top so that I could put 2 layers of half inch FB board... all I could find. Trying to figure out how to upload pics but can't... technology not my strength.

[Cadott]

Re: Kastolite 19

After test fires, the 3.5" of Kast O Lite 19 (kastolite) is NOT enough insulation under the firebrick floor. The hearth would not go above 650F. The temperature of the steel plate supporting the oven rose from 35F to 135F in two hours. Too much heat is being lost through the bottom. To correct, I plan to install insulating board under the firebrick. I think the kastolite makes a great base, it just needs insulation board to complete the heat barrier.

[david s]

Re: Kastolite 19

After test fires, the 3.5" of Kast O Lite 19 (kastolite) is NOT enough insulation under the firebrick floor. The hearth would not go above 650F. The temperature of the steel plate supporting the oven rose from 35F to 135F in two hours. Too much heat is being lost through the bottom. To correct, I plan to install insulating board under the firebrick. I think the kastolite makes a great base, it just needs insulation board to complete the heat barrier.

Sounds like you still have moisture in your kastolite layer.Additional insulation won't hurt, but more firings might tell you another story.

[Cadott]

Re: Kastolite 19

I gave the oven another test burn and the heat loss through the bottom was still significant. Instead of more burns, I decided to remove the firebrick floor and install a 1 inch insulation board over the 3.5 inch Kastolite 19 base. After putting the firebrick back in, I gave the oven another firing. This time, the bottom steel support plate only gained 30 F degrees over eight hours. This is a huge improvement over the 150 F plus gain I was seeing before.

My conclusion: Kast O Lite 19 makes a great base but 3.5 inches is not enough to stop heat loss. Moisture may still be in the Kast O Lite 19 causing the heat loss, but I don't want to burn a pile of wood to find out.

Hope this helps someone down the road. Good luck.