Questions about curing and firing

[Bleu86]

I've been trying to find a solid answer to this all morning and haven't been able to pin anything down.  I plan on completely sealing all of my ceramic blanket with Kastolite 30, and coating that with Plistix.

I see people talking about firing their insulation to get it to really set.  Is that necessary if it will be sealed, or can I let it air cure? 

Same question for the refractory and kiln wash.  Do I need to fire the refractory first or is it fine to just let it sit for a few days.

Finally, I know I should butter each layer of the insulation, should I butter the refractory before applying the kiln wash?

Thank you for any advice, hope you're all staying safe!

[Frosty]

Get's confusing doesn't it Bleu. Unless you know what folk are talking about it's hard to separate the different steps being discussed.

When you read about flame curing the blanket before covering it with the hard refractory Kastolite in this case. They are referring to heat curing rigidizer used to stiffen the ceramic blanket and encapsulate the fibers so they can't break off and float around your breathable air. 

Other folk talk about heat curing Kastolite 30 which isn't necessary as such. Bringing the forge to low red and letting it cool then heating it again but hotter is mostly to drive the moisture trapped in the refractory blanket off. 

Kastolite (KOL) is strongest and most heat resistant if it's cured the same way you would a concrete floor. The calcite in the binder hydrates when mixed and sets. After it sets it's cures to it's strongest in 100% humidity. These are what the guys are talking about sealing their forge in a plastic bag with a wet towel for 1 to 7 days. 

When it's done wet curing is a good time to heat it up a couple times to below forging temps to dry the blanket out. ceramic blanket absorbs and holds water like a sponge, just because it's not dripping doesn't mean it's not sopping wet.

Yes, the kiln wash is the last thing to go on, after wet curing the KOL. Mix it to latex paint consistency, no thicker and apply it in multiple thin coats allowing it to dry between coats. If applied correctly all you need do is let it dry thoroughly and it's ready to go to work. It will fire like ceramics in the forge but you don't have to do anything special for it, just dry and put it to work.

A last note here that applies to any time you use a form of cement type produce, from masonry mortar up to kiln washing the forge. You need to wet the layer you're coating first, it's called "buttering." This allows the binders in the various products to bond fully with the subsurface they're being applied to. It's important, don't forget.

Frosty The Lucky.

[Ironwool]

Thanks Frosty this really cleared up the process for me as well. First time posting but this site has provided a ton of information so far, so thank you to everyone for sharing your knowledge.

The "buttering" you are speaking of would that be with a thinned down Kastolite, closer to maybe honey then peanut butter?

[Frosty]

You're welcome, it's my pleasure. Buttering masonry work refers to wetting it down before applying any adhesive material. In this case we are bonding: rigidizer,, hard refractory or kiln wash to a masonry material. Hardened Kastolite or ceramic blanket fall under the definition.

What happens if you apply wet material to dry is the dry material draws the moisture leaving a layer of dry between the two. Say, Kastolite over Kaowool. The Kaowool dries the contact layer leaving the contact points with a layer of dry powder between them. This prevents the kind of bond necessary to stick bricks or Kastolite to a surface. 

Buttering wets the surface so when the "cement" is applied it is diluted slightly and drawn into every nook and cranny making as strong a bond as possible. Buttering blanket before rigidizing also causes the rigidizer to flow along the fibers and concentrate at intersections. When the moisture dries out the fumed silica remains and when fired solidifies gluing fibers in place which makes the blanket more rigid.

Make sense?

[JHCC]

Yes, do not neglect the buttering and don't underdo it. I did not butter the ceramic wool in my first gas forge, and now the Kastolite is coming off in chunks. I plan to reline it at the same time that I put the Kastolite lining in my new gasser, and will definitely be less stinting with the spray bottle.

[Irondragon Forge ClayWorks]

Buttering is done with plain water by the way.

[Gee]

Hey guys,

 

Thank you for the detailed information here.  Can you direct me on how wet the blanket should be before applying the Kast o lite?  Soaking wet! Top layer wet?  Moist all the way through?

Thanks. 

[Frosty]

Just spritz it down good, sopping wet is overkill but isn't going to ruin it. 

Frosty The Lucky.

[Gee]

Thanks Frosty. As you have been told before...thank you for your expertise in teaching and helping all the rest of us!

[Frosty]

You're welcome Gee, it's my pleasure. I figure the more guys we can get up to speed and making stuff the more eye candy pictures we'll get to look at. 

Frosty The Lucky.

[Gee]

Absolutely. I can’t wait to get to making some stuff myself. 

[Madam Waffles]

Just to continue the questions... does rigidizer for the ceramic wool need to go on the cold face in between the blanket and the shell? Or should one just put the blanket in the forge, butter, and apply rigidizer to exposed faces for every layer?

Additionally, when doing a layer of kast-o-lite: I have a hexagonal foundry, will the “cement” be able to handle 60 degree inclines or should I really do one face at a time...

[Gee]

I used a ceramic 2” blanket. Covered that with Kast o Lite using a form I made. It worked great. Final step is to apply my kiln wash. In this case I am using Plistix. Haven’t gotten that far but almost there.  If you are using Kast o Lite over the cearamic wool, then this would be considered ‘ridgidizing’ from my understanding. Ridgidizing is the process of encapsulating the blanket to hold it in place and from falling apart.  If I am amiss, someone please correct me about ridgidizing. See attached pics of my forge. 
 

-Gee

[Frosty]

1 hour ago, Madam Waffles said:

Additionally, when doing a layer of kast-o-lite: I have a hexagonal foundry, will the “cement” be able to handle 60 degree inclines or should I really do one face at a time...

I'd do the bottom half and let it set before rolling it over and doing the other half, Kastolite will sag if there is much overhang. My current forge has a wonky floor because I got in a hurry and didn't let it set before flipping it over to do the rest. 

Don't worry about it sticking to itself, Kastolite is demonically sticky. Butter it anyway though. 

Frosty The Lucky.

[JHCC]

12 hours ago, Gee said:

If you are using Kast o Lite over the cearamic wool, then this would be considered ‘ridgidizing’ from my understanding. Ridgidizing is the process of encapsulating the blanket to hold it in place and from falling apart.

Not quite. Rigidizing is wetting the ceramic wool blanket with a mixture of water and colloidal silica and then firing it as described above. The heat fuses the fine particles of the colloidal silica and the ceramic fibers together, forming one rigid (if very porous) mass. This has two benefits: it gives the blanket somewhat greater structural strength, and it keeps fine particles of the blanket from breaking off, getting into the air, and getting into your lungs where they can cause some pretty nasty health problems.

Using a mold the same shape as the finished interior is a great way to install the Kastolite. On my last forge, I used a mold of 1/8" Masonite with internal bracing that could be assembled and disassembled in place; it worked great.

[Madam Waffles]

1 hour ago, JHCC said:

Using a mold the same shape as the finished interior is a great way to install the Kastolite. On my last forge, I used a mold of 1/8" Masonite with internal bracing that could be assembled and disassembled in place; it worked great.

Masonite! Great idea. I was thinking plywood, haha.

[JHCC]

It was what I had lying around, but it worked great. I know others who have used scraps of linoleum with good success.

[Frosty]

Kastolite will bond to bare wood it literally tore the wood form apart the one time I tried it without sanding, painting then greasing. It is demonically sticky, no exaggeration!

Frosty The Lucky.

[Gee]

I wouldn’t use regular plywood. It is highly porous and therefore Kas o lite will adhere to it. I used sheet metal duct for mine. Purchase a 7” round tube for $6. Shaped it how I wanted it. It worked great. With a little pulling it came out nice with no sticking to the Kast o Lite....

[Gandalfgreen]

When doing the silica stage if I let it air dry longer then a day before I fire it will it affect the end result. Mainly asking wanted to coat it today but not sure if have time tomorrow or next day to fire cure it.

[Frosty]

If you're rigidizing with fumed silica you don't have to let it dry before flame curing it. 

Frosty The Lucky.

[JHCC]

This is true. 

[Judehey]

For flame curing the silica, how hot?  How long? What should I be looking for? 

Thanks

[Frosty]

Red hot for a bit, 30 seconds or so.

Frosty The Lucky.

[Judehey]

Thanks Frosty

In another post you said "reasonably dry". Is overnight appropriate? Is too dry bad? 

Thanks again