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How to Kast-o-lite 30 and Kaowool Scraps

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So I ordered some Kast-o-lite but I'm a little confused with the directions I've found online-- the actual Kast-o-lite didn't come with directions. Could I get some help? What steps should I take to cast it?

Also, will Kaowool get soaked up with wet Kast-o-lite?

Would using Kaowool in the refractory help at all or not really?

Also- If I cut up a bunch of scrap Kaowool and mixed it in randomly with the refractory (Kast-o-lite) wound that help the insulation of my forge?

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Which % Kast-O-Lite did you pick up? After the input by folks here I decided to go with Kast-O-Lite 30. I haven't looked the bag over though so we may be in the same boat looking for mixing directions. We want it as dry as possible and still get it to fill the form completely. If you're going to use it in a trowel on application you need to  mix it wet enough to spread smoothly.

No, mixing Kaowool in the refractory will NOT improve it's insulation properties. It shouldn't soak into ceramic blanket unless you've mixed it WAY too wet. Remember, the wetter you mix it the weaker it becomes and the lower it's insulating qualities. I really wish I remember the site with all the details, probably the manufacturer's site or one affiliated. IIRC it had mixing % for different applications but they are based on a full bag so a little arithmetic to convert to the size batch you're mixing is in order.

Frosty The Lucky.

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I picked up Kast-o-lite 30, I heard the best things about 30 so I ordered some. I've got 20 pounds of it and upon further research I saw a post about maintaining the mix after you open the bag- does it harden up when exposed to air or something?

Also, is Kaowool at least a good forge backer if your using refractory, can they be used together at all?

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Kaowool is an excellent forge insulation layer, the Kastolite is a higher efficiency refractory layer, which does not substitute well for the forge insulation recommended (if you want an energy efficient forge lining).  The Kastolite gives you a more durable and less friable surface than the Kaowool alone (reasonable protection from molten flux if the high alumina version is chosen and virtual elimination of loose fibers that get released from the "cooked" Kaowool).  It also gives you a better flame impingement resistance, potentially allowing the use of lower temperature rated Kaowool (say 2300 degree instead of 2600 degree) depending on the thickness of the Kastolite and the proposed interior temperatures you plan on having for your forge.

There are several different ways to use the two materials in concert to make a multi layer forge lining.  Here are two that I have used successfully:

  1. Inside to outside: Cast the refractory interior independently using removable forms.  Allow to cure, remove forms, and heat slowly to drive off moisture then run up to full hardening temperatures following the manufacturer's instructions (if instructions not available I would let it cure overnight, then heat in a kiln slowly up to 400 deg. F with the lid ajar to allow moisture to drive off - think hours here-, then ramp up to say 1400 deg. F at a rate of say 200 deg. F per hour).  Other methods to preheat and final cure can be used, if a large kiln is not available.  Then wrap the inner refractory with 2" of six or eight lb. density high temperature Kaowool blanket.  Then wrap the blanket with a metal skin.  Be sure to cover any loose Kaowool.  You can also just loose pack the kaowool between the metal skin and the inner refractory if you have a good skin selected (this works great for using Kaowool cutoff scraps and loose insulation that are at times available free from industrial insulation suppliers).
  2. Outside to inside:  Assemble metal skin with all burner ports.  Line inner side of skin with 2" of Kaowool blanket (or two 1" layers with staggered seams).  Lightly spray wool with water then coat kaowool with several layers of colloidal silica solution and let this set till hard.  Mix kastolite refractory using the "loose ball method" (premix dry material by hand, slowly add water portion constantly mixing and testing - be careful it is easy to have too much water for this-, test with loose ball method by taking handful of the mix, lightly compressing it in your hand then tossing a couple of times up into the air around 5 inches above your hand.  If it breaks apart you need more water, if it holds together and further compacts, you are there.  If it runs through your fingers you have put in too much, start over...) and coat the interior of the forge with at least 3/4" thickness of this material (can lay on side and mortar in place this in two halfs or use removable interior form - if latter allow for shrinkage). 

In either case allow for your burner ports when casting and consider an IR reflective coating on the refractory as a nice addition for additional efficiency.

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Here are the directions I used when building my forge

ANH Refractories Company
Mixing & Using Instructions


--------- GENERAL INSTRUCTIONS --------
Material should be stored in a dry place. For best results, material should be
maintained at 50-70F prior to casting. Under these conditions, the maximum
recommended storage life for this product is twelve months.

Porous back-up materials or wood forms should be waterproofed. Absorption of water
can result in reduced flow for the product. Forms must be stout and water tight.
This product is designed to be mixed with water and then poured/handcast into place.
All equipment used to mix this product must be clean.

Never mix less than full bags. Add only clean water suitable for drinking with a pH
value between 6.0 and 7.5. For best results, water should be maintained at 50-70F.

--------- MIXING REQUIREMENTS ---------
Approximate Water For Installation Pints (Liters)

Bag Size                                                      Poured/Handcast                       
100 lbs. (45.5 kg)                                        17.2 (8.1)
55 lbs. (25.0 kg)                                            9.5 (4.5)
50 lbs. (22.7 kg)                                            8.6 (4.1)
Wt. % of dry solids 18.0

Mix for at least three minutes. For best results, wet mix temperature should be
maintained at 60-75F. Minor adjustments to the amount of water are permissible to
achieve desired flow.

--------- INSTALLATION ---------
Place material promptly. Do not trowel to slick finish. At temperatures above 60F, air
cure, keeping surfaces damp and/or covered, for 16-24 hours typically or until a hard
set has developed. Lower temperatures will increase the time before a hard set
develops. The best results are achieved at curing temperatures of 90-110F. Keep
material from freezing during air cure and preferably until a dryout can be initiated.
Freezing of this product prior to water removal can cause structural damage.

-------- HEAT UP SCHEDULE --------
Never enclose a castable in a vapor-tight encasement as a dangerous
steam explosion may result. Typical dryout schedule for a single layer, 9"
(229 mm) thick or less:

ambient to use temperature 100F (56C) per hour

For thicker or multi-layer linings, contact your Harbison-Walker representative
for a recommended dryout schedule.

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Thank you John. Did you use any special procedure for firing the first time or two? I recall seeing different strength, densities and insulating properties for different "cure"(?) temperatures.

I recognized he first cure temperature, 230f min - 300f. as intended to drive off any residual hygroscopic moisture after chemical reactions are complete. OR I could be completely mistaken.

 Frosty The Lucky.

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No Frosty, I really didn't. Life is busy and time is tight. After ramming the Kast-o-lite in, the forge had to sit for a couple of weeks before I could get back to it. I put a space heater on it for the second  and third day. It was pretty dry before my first firing. Then not having a way to measure temperature ramps, I just set the burner on very low for an hour or so and then cranked it up trying to guestimate 100F per hour to maximum temp. Not very precise, but the Kast-o-lite cured very hard and didn't crack at all. So I got lucky with it. I'd rather be more precise, but I just didn't have the equipment to do so.

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I don't know that you got lucky with it I think you were well enough within it's working range it came out fine. The part of the instructions about keeping it damp says to me the calcium component is working like burnt lime does in Portland cement, it isn't drying, it's forming a chemical bond.

Bringing it up to temp gradually as you did is a good method for driving off unbound hygroscopic moisture and preventing steam spalling or explosions. I'll be doing similar when I start using it. I have both the forge and a ribbon burner to make. The ribbon is taking some experimentation but I think I have it close enough for a proper test ribbon.

Thanks. Frosty The Lucky.

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