BHGiant Posted July 23, 2020 Share Posted July 23, 2020 To get used to the materials, I made a miniature forge from a paint can. Placed the kaowool two layers thick with rigidizer and then coated the wool with refractory. Here is the product. I heated the forge very gradually in my oven constantly checking on it. I left it at 500° for several hours (instructions said for at least one) and left it to cool afterwards. It was undamaged the entire time. When I took it out after it cooled, it looked like this. Lots of cracking. What went wrong? What do I do different next time? Is this salvageable? Link to comment Share on other sites More sharing options...
Frosty Posted July 23, 2020 Share Posted July 23, 2020 You used refractory CEMENT. It is made to stick things together like bricks NOT survive flame contact regardless of the temperature rating and you didn't even get the 3,000f cement. Not that it would've been much more successful but it probably would've survived curing. You need to use a water setting, castable REFRACTORY of suitable temperature rating. Current favorite being Kastolite-30-li. It is a "3,000f. water setting, high alumina, castable bubble, refractory." What all that means is. Water setting, means water causes bonds between particles that contain molecular water. It does NOT DRY like pottery, it sets like Concrete. Castable means it can be formed in a mold, again LIKE poured concrete. While not easily it trowels well enough. Having an alumina content makes it more resistant to caustic forge welding fluxes like those containing borax. It won't just dissolve when molten borax gets on it. Last are the bubbles which are evacuated silica spheres that lower the weight and reduce heat transfer through the hard inner liner. They make Kastolite an insulator. Next time? Pick one of the proven forge designs and follow it. "Forges 101" is the most current collection of discussions regarding forge building. Frosty The Lucky. Link to comment Share on other sites More sharing options...
BHGiant Posted July 23, 2020 Author Share Posted July 23, 2020 Any idea why the cracking Frosty? It never came in contact with a flame. Link to comment Share on other sites More sharing options...
Frosty Posted July 24, 2020 Share Posted July 24, 2020 It's probably pretty wet so it shrank as it dried and checked like a dry mud puddle. Being a thin cot on a soft surface may have promoted it flaking. I've never had occasion to use a refractory cement, the closest I ever came was when Dad mortared a couple of loose bricks in the fire place and he mixed his own. IIRC it was mostly lime, little sand and a maybe a capfull of Elmer's glue in the water. He mixed it pretty thick and let me hold the light for him at a distance. I was maybe 8-9 so I probably missed a secret ingredient even though he told me the what and why of everything he did. Said lime mortar would take the heat better than Portland cement mortar. Frosty The Lucky. Link to comment Share on other sites More sharing options...
Mikey98118 Posted July 24, 2020 Share Posted July 24, 2020 In any case, the damage is minor at present. Nothing prevents you from following his advice, and casting a layer of Kast-O-lite 30 inside of the cement, and proceeding with construction. You can buy small amounts of the refractory right here. Look up at the top of the list. Link to comment Share on other sites More sharing options...
BHGiant Posted July 24, 2020 Author Share Posted July 24, 2020 23 minutes ago, Mikey98118 said: Nothing prevents you from following his advice, and casting a layer of Kast-O-lite 30 inside of the cement Ok, so it's still salvageable even with the cracks. And it sounds like I'll need to make the mix thicker (less water) in the future to avoid those cracks. Just so you all know, this is a "test" forge. Something I'm putting together to get used to the materials and the process and make mistakes with. I figure it's better to make the mistakes with something cheap and learn from it. I appreciate the insight. Link to comment Share on other sites More sharing options...
Frosty Posted July 24, 2020 Share Posted July 24, 2020 Kastolite will be a test to apply, the aggregate is crushed so it keys together and is NOT easy to trowel or smooth. Check the cracked cement to see if it flakes or falls off easily. If so then you'll want to get as much out as you can to prevent it flaking and making the new liner break up and fall off. Make sense? Sorry I forgot to say your test forge is salvageable. Guess I've talked about mortar and cements making bad refractories too many times. Frosty The Lucky. Link to comment Share on other sites More sharing options...
BHGiant Posted July 25, 2020 Author Share Posted July 25, 2020 I hear that. There's soooooo much bad advice on the internet. Before I found this forum, I was playing around with Portland cement and perlite on the advice of some pizza oven enthusiasts. I made some bricks and they were decent at insulating but (obviously) crumbled at forge temperatures. I'm sure you will be relieved to hear I have given up on cements as a suitable refractory :). I had bought the Rutland product before I found this forum so having the sunk cost already, I figured it would be a good way to see how it might hold up. The good news is the flakes are very strongly adhered to the kaowool+rigidizer underneath. So much so that trying to take them off would rip the kaowool out with it. I think I'll buy some Kastolite and see how covering it over goes. Link to comment Share on other sites More sharing options...
Mikey98118 Posted July 25, 2020 Share Posted July 25, 2020 shame on you, Frosty. You didn't tell him to wet the cement layer first Link to comment Share on other sites More sharing options...
Frosty Posted July 25, 2020 Share Posted July 25, 2020 You know Mike, if you knew my friends you'd understand why I'd never suggest wetting something! You're right though, I'm really slipping helping this fellow. Butter the existing cement liner before applying the Kastolite BH. Buttering is spraying or otherwise wetting it down so the next layer will bond properly. If you apply a mortar of any kind to a dry surface the contact layer will flash dry and not set and cure so there will be a layer of dry powder between the two. Buttering puts extra moisture on the contact surface so when the mortar is applied the contact is diluted and flows into all the nooks and crannies. The extra moisture also provides full hydration for the cure. In this case mortar, portland cement grout, Kastolite, whatever behaves in the same way so don't be confused by me using "mortar" in the above description. If you've ever watched a mason lay brick you've seen him butter the brick by dipping it in a bucket of water and the wall with a brush and water before applying the mortar. Better MIke? Have I missed anything else? I'm starting to wonder where my head's at today. Frosty The Lucky. Link to comment Share on other sites More sharing options...
Mikey98118 Posted July 25, 2020 Share Posted July 25, 2020 Very good Frosty. We aft to keep up your standards, after all Link to comment Share on other sites More sharing options...
Frosty Posted July 26, 2020 Share Posted July 26, 2020 Thanks Mike, I need help. . . What were we talking about again? Frosty The Lucky. Link to comment Share on other sites More sharing options...
BHGiant Posted July 26, 2020 Author Share Posted July 26, 2020 You guys are awesome . And I appreciate the crash course. I was talking to Glenn Friday night. He was bragging on all of you and I have to say I'm honored to have your input and advice. He was giving me some more pointers on safety and making sure I wasn't blowing myself up or sucking crud into my lungs. Told me a bit more about the story with PawPaw. Such a sad story. So unfortunate. Talked about galvanized coating some more and to be extra careful with fumes in general. He's going to pack me up some Kast 30 and Plistix and send it to me on Monday... That is, if the delivery truck can ever find his shop . I'll be sure to give the inside layer a good buttering before I apply. Link to comment Share on other sites More sharing options...
Frosty Posted July 26, 2020 Share Posted July 26, 2020 2 hours ago, BHGiant said: You guys are awesome Yes, we're aware of that, thank you. Mike and I gave Glenn $1.50 to brag us up like that. Actually, we're good with common courtesy, I'm not big on taking myself too seriously. Safety is another matter though, I'm glad Glenn spent some time talking safety with you. Next time you talk to Glenn, tell him if he didn't have to keep the revenuers guessing, UPS wouldn't have so much trouble. Frosty The Lucky. Link to comment Share on other sites More sharing options...
Mikey98118 Posted July 27, 2020 Share Posted July 27, 2020 I t only cost you a buck and a half? Glenn always liked you best Link to comment Share on other sites More sharing options...
Frosty Posted July 27, 2020 Share Posted July 27, 2020 Link to comment Share on other sites More sharing options...
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