I hope it's not too forward but the info Frosty provided in this same thread on Nov 9, 2017 is so helpful to amateurs I wanted to compile it into a bullet pointed list that might be helpful. From the info Frosty provided the bullet points below are just an extraction of his info into an outline. There are two deviations from Frosty's info (noted) in the steps with explanation for the deviations. The deviations may not be valid but throwing them into the mix in case anyone can confirm whether they are/aren't valid to include.
I'm an amateur who bought a furnace from a great guy who runs the backyard metal casting site and have built some custom small amateur forges and a waste oil burner but haven't yet really put any of it to productive use - mainly due to the day job. Thanks.
STEPS TO LINE WALLS OF FURNACE/FORGE INTERIOR
- DEVATION FROM FROSTY'S INSTRUCTIONS:
- brush a coating of sodium silicate onto the inside metal interior of the furnace
- REASON FOR DEVIATION: just for adhesive to bind the kaowool to the metal
- First layer of kaowool:
- line a 1" layer of kaowool around the inside metal interior of furnace - sticking it to the sodium silicate
- rigidize the first layer of kaowool
- mix 1 cup Colloidal silica with 1 pint clean water and add the mixture to a spray bottle
- Spritz the kaowool with clean water first to butter it - this will allow the colloidal silica rigidizer to penetrate more deeply
- Spritz the kaowool with the rigidizer
- Fire cure the outside layer now, a Bernzomatic torch will do the job nicely, just bring it up to red heat, that's plenty.
- Second layer of kaowool:
- prepare a second 1" layer of kaowool that will be placed on top of the first layer of kaowool
- before placing second layer on top of first layer:
- spritz first layer with clean water
- spritz the side of the second layer that will set against first layer with clean water
- spritz the side of the second layer that will set against the first layer with rigidizer
- place the second layer on top of the first layer, with the side of the second layer that has been rigidized set against first layer
- rigidize the inner surface of the second layer of kaowool
- Spritz the kaowool with clean water first to butter it - this will allow the colloidal silica rigidizer to penetrate more deeply
- Spritz the kaowool with rigidizer
- Fire cure the second layer now, a Bernzomatic torch will do the job nicely, just bring it up to red heat, that's plenty.
- Press the liner with your finger, it shouldn't compress without pressing hard. If it does compress butter and rigidize it again.
- Once the insulating outer liner (Kaowool) is dry and flame cured, cut your burner port(s).
- I use a sacrificial hole saw, don't hog it and it won't tear the rigidized Kaowool.
- Drill it over sized so you can plaster it with the flame face refractory.
- DEVATION FROM FROSTY'S INSTRUCTIONS:
- apply coating of Matrikote to inside face of rigidized kaowool
- Let the Matrikote dry and flame cure it to red heat, let it cool.
- REASON FOR DEVIATION: if radiation can indeed absorb through refractory, this coating of Matrikote would be an added layer to
reflect the heat back to inner furnace.
- Once you have all the mechanical mods made it's ready to lay in the hard refractory flame face. Recently "Kast-O-Lite-30 hi." has
become the popular consensus "best stuff." It's a castable, 3,000 f. high alumina, bubble refractory. It is concrete hard at
it's top operating temp 3,000 f.
- Mix the refractory with only enough water to make it workable (The wetter you mix it the weaker it is when cured.)
- Butter the kaowool and plaster it approx 1/2" thick with the hard refractory.
- Once set the recommendation is to keep it at 100% humidity between 70 f. - 120 f. I just wrap my castings in a wet towel and give it
over night to finish setting and do some curing.
- apply coating of Matrikote to inside face of rigidized kaowool
- Let the Matrikote dry and flame cure it to red heat - mount your burners bring it to red heat, let it cool.
- It's ready to go to work.
