Anyone who's troweled Kastolite 30 into a forge knows it's a PITA. A question has come up recently that needs something easier to apply but has similar characteristics, temp, flux resistance, etc. I've been looking at water setting castables and Mizzou fits the bill, lacking only Kastolite's insulating characteristics.

So my question is for folks who've used Mizzou. How does it trowel? Is the aggregate in it rounded/smooth or crushed/angular?

Thanks all.

Frosty The Lucky.

I've used Mizzou, but not casted anything with it for over 20 years, so going by dim memory here.  I used it to cast burner blocks and did some light troweling into the bottom of my ceramic blanket glassblowing glory hole for molten glass resistance.  I don't recall it troweling any better than Kastolite, and I've never tried to do successive sections of either to build an arch from a series of installations.    

I have troweled  Greencast 97 over the top of a large clay form to make an arch for the top of my glass furnace. That worked very well, though the form had to be removed carefully while the refractory was setting.  I did add SS needles to the dry mix for that, which made it not a whole lot of fun to mix up by hand.

Personally I'm in favor of casting the inner skin of the forge in Kastolite with a removable inner form.  This is certainly feasible in 3/4" thickness, which IMHO is a good compromise for an inner liner.

I have some Greencast 97 as a matter of coincidence and I do remember it being much easier to manipulate, eg. trowel. 

I'm thinking for the purpose I'm sort of consulting on, I'd alter the forge so a precast hard liner could simply be slipped in. Two part, combined wall and roof over a single piece floor. The burner port could be tapered to act as the burner flare even and the buyer could just fire it up. Cost them more but it has it's advantages. 

It's how I made my first propane forge, I cast the hard liner between Sono tubes with 3/4" annulus between them and drilled the burner port before it'd set completely. Once set and cured I pealed the outer and burned the inner one out.  Were I to do similar now I'd use a piece of linoleum for the inside form and pull it.

Frosty The Lucky.

Another alternative would be too do something like what Tim Zowada does with his forge kits:

That's the basic idea I'm thinking about, a precast inner liner might be easier on everybody. 

Frosty The Lucky.

There are some engineered ceramics companies that produce custom high alumina crucibles and other specialty components.  Might be able to go to them for a custom casting, but I suspect it would be prohibitively expensive.  Here are some from Selee:

Yeah, those options would be prohibitively expensive for sure. Morgan Thermal Ceramics sells K-26 in all sorts of shapes other than brick, including custom. But again prohibitive and I don't think the route they want to go. Still something to look, into and suggest for consideration.

Thank you. 

Frosty The Lucky.

Has anyone tried using the "G" version of Kastolite 30 LI? According to the retailer up here:

• The 'G' stands for 'gunning mix'. This makes it easier to apply up the side of a forge as it does not slump like casting grade. It will have slightly less of a compression grade, but in a forge this is not an issue.
• Kast-O-Lite 30 LI G is a lightweight, insulating gunning castable rated to 3000°F. It has great insulating qualities similar to the Kast-O-Lite LI 30 PLUS however, it has a higher lime content. This means it sets up/hardens quicker (5-10 minute work time) compared to Kast-O-Lite 30 LI Plus' (30 minute work time).

How fast can you apply that much Kastolite? 20-30 minutes isn't enough time sometimes, I can't imagine having to do it in 5-10. I do it in stages to avoid sag I've never seen Kastolite slump, not even on a trowel held vertically.

Frosty The Lucky.

I won't be ordering that then, thank you.

Edited October 28, 20223 yr by Mod30
Remove excessive quote.

On 7/25/2022 at 12:48 PM, Latticino said:

Personally I'm in favor of casting the inner skin of the forge in Kastolite with a removable inner form.  This is certainly feasible in 3/4" thickness, which IMHO is a good compromise for an inner liner.

Total agreement here. In small forges, I started out using a grocery store size salt container, wrapped in tape for the inner form. Glass jars are probably the simplest way to go, as they shatter into small pieces after heating up to red with the burner, and then allowed to cool down; Just dump the pieces into a trash container, and the inner form is gone

I always got smooth inner surfaces by casting, and that without even vibrating the form; I'm looking forward to adding that trick on the next few pieces of equipment.

That's a very clever trick that I never thought of or heard of before.  Me a former glassblower who should have known.  I'll remember that one.

Same.