How Much Kastolite to Mix Up?

[Fishgod]

I am close to getting ready to put the Kastolite 30 over my rigidized wool liner.  I have 10# total just to make sure I have enough.  My forge is a 20# propane bottle.  Without the Kastolite I am at approx 350 cu inches.  What do you think 3lbs, 4lbs ?

[JHCC]

What you need to do is calculate the volume of the hard refractory shell (roughly the area of the surface to be covered times the intended thickness) in cubic inches, and then divide that by 19.2 (the number of cubic inches in a pound of mixed kastolite). That will give you a number for how much to mix up, assuming that you're casting in one piece. If you do sections, divide the total volume by the number of sections you want, and mix accordingly.

[Fishgod]

Thanks for giving me the formula and forcing me to figure it out.  If I am correct it would look like the below

Surface area 7x9 

275 x .25 / 19.2 = Pounds of Kastolite

Rounded up I come up with 3.6lbs
 

Does that look right?

 

[Frosty]

Round it up farther. Just have a couple things you can use the excess on ready. Say the door baffles. Kastolite will patch missed or thin spots well but it's better to not have to. Mixing a small batch is harder than a larger one. 

Frosty The Lucky.

[Fishgod]

Thanks all.  I commited the cardinal sin.  I didnt butter the wool so i could only complete about half of the forge. The side walls and floor are covered along with part of the door and pass through.  Lesson learned.  I did 2.75 ounces per pound.  I have the forge in a plastic bag with a wet towell.  I wont touch it until Friday. I will hopefully finish off the rest of the forge then.  I did get everything welded up tonight.  I was quckly reminded that I really dont know how to weld.  But hey thats what an angle grinder is for :).