iamjoe Posted March 2, 2017 Share Posted March 2, 2017 So after a few years of wishing, I finally built one. I used ceramic blanket for lining, 2 inches. I've read a lot of information on forms to get to this point. Thanks everyone. The more I read, I am under the impression, that for safety reasons I need to coat the ceramic blanket. There are no shortage of discussions, opinions, or options on coatings. My only concern, however, is safety. What is my cheapest option to make my forge safe to use? Right now I just don't use it enough to be hung up on efficiency. I can be hot enough to forge in just a few minutes. Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Latticino Posted March 2, 2017 Share Posted March 2, 2017 My recommendation would be an initial coating of colloidal silica to stiffen the blanket, then a final coating of refractory. There are many options for the final coating: 3,000 deg. F rated furnace cement: cheapest option and readily available at big box hardware stores. Apply in multiple thin coats to build up to at least 1/4" thickness. Down side is that it is rather fragile and prone to cracking away from the surface. Mizzou refractory: rated for the temperatures expected and fairly resistant to flux. Downside is that it is not as easy to source, more expensive than furnace cement, needs to be cast in place in one monolithic section, if possible, and may crack from thermal cycling. Also typically a minimum thickness of 1/2" will add more thermal mass to your forge, but if correctly installed and cured should last for decades. High Alumina castable refractory (Greencast 97 or similar). Same as Mizzou, but even more expensive, harder to source (go to industrial refractory suppliers and ask for a "sample") and flux resistant. "Bubble" Alumina Refractory: Lighter, flux resistant and even more expensive. I have limited experience with this material, but did use it in the bottom of one of my gas forges for flux resistance to good effect. A final inner coating of a IR reflective material (ITC 1000, Plistex, Metricote...) is reported to make the forge more efficient, but needs to be renewed periodically. Quote Link to comment Share on other sites More sharing options...
iamjoe Posted March 2, 2017 Author Share Posted March 2, 2017 Just a quick search for colloidal silica show liquid and a gel. I'm currently at work so I have limited time for research. Which would work? My inside wrap of blanket was approximately 12 x 20 inches. How much would it need? Quote Link to comment Share on other sites More sharing options...
WayneCoeArtistBlacksmith Posted March 3, 2017 Share Posted March 3, 2017 I suggest that you cast over the blanket with about 1/2" of Kast-0-Lite castable refractory and then paint over that with Metrikote IR. If you really want to go cheap just paint the Metrikote over the blanket but because Metrikote is not a tough surface you will constantly be repairing it. Check out the attachment Build a Gas Forge at the Forge Supplies page at www.WayneCoeArtistBlacksmith.com. Let me know if I can help you. Wayne Quote Link to comment Share on other sites More sharing options...
Frosty Posted March 3, 2017 Share Posted March 3, 2017 Use liquid rigidizer not a gel. Spray the blanket with water before applying to prevent it from flash drying on contact and not penetrating or adhering properly. You don't really want the cheapest product you want the best you can afford. Talk to Wayne about small quantities for reasonable. He'll help you determine how much you'll need. By help he'll instruct you in how to calculate these things yourself. Having other people do things FOR you isn't very blacksmitherly you know. Having someone show you is something else entirely. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
iamjoe Posted March 3, 2017 Author Share Posted March 3, 2017 First let me say thanks for all the information. I appreciate people who are willing to pass on their experience and knowledge. Also, thanks for your patience. I know this topic must get old. There are almost as many options as opinions out there. Makes it hard to sort through. Especially when my main concern is simply safety and not the hundred other potential considerations. Any suggestions for rigidizer? Quote Link to comment Share on other sites More sharing options...
AnBello Posted March 3, 2017 Share Posted March 3, 2017 22 minutes ago, iamjoe said: First let me say thanks for all the information. I appreciate people who are willing to pass on their experience and knowledge. Also, thanks for your patience. I know this topic must get old. There are almost as many options as opinions out there. Makes it hard to sort through. Especially when my main concern is simply safety and not the hundred other potential considerations. Any suggestions for rigidizer? You might have misunderstood the previous replies. I believe the liquid (not gel) Colloidal Silica is the rigidizer itself. Quote Link to comment Share on other sites More sharing options...
iamjoe Posted March 3, 2017 Author Share Posted March 3, 2017 "You might have misunderstood the previous replies. I believe the liquid (not gel) Colloidal Silicais the rigidizer itself." Sorry for not being more specific. I was curious to a specific brand or type for forge application. I know nothing about the product. I was fishing for a direction to research more. My lack of knowledge about it is probably very obvious. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted March 15, 2017 Share Posted March 15, 2017 Brands? Most of this stuff is made up at the ceramic supply store you will buy it from. It is cheap and easy to procure this way...unless you have no such source handy. Then, you can buy fumed silica through eBay and mix it with water yourself. Use a cleaner bottle with a built in spritzer top to apply it the easy way. I suggest adding food coloring dye to easily see how deep the rigidizer is progressing into the ceramic blanket. If you mix it too lean add more silica; if it is too thick add more water. All of this is simple, so please don't freeze up and complicated it. Speaking of freezing avoid allowing your mixture to to so. Quote Link to comment Share on other sites More sharing options...
iamjoe Posted March 16, 2017 Author Share Posted March 16, 2017 4 hours ago, Mikey98118 said: Brands? Most of this stuff is made up at the ceramic supply store you will buy it from. It is cheap and easy to procure this way...unless you have no such source handy. Then, you can buy fumed silica through eBay and mix it with water yourself. Use a cleaner bottle with a built in spritzer top to apply it the easy way. I suggest adding food coloring dye to easily see how deep the rigidizer is progressing into the ceramic blanket. If you mix it too lean add more silica; if it is too thick add more water. All of this is simple, so please don't freeze up and complicated it. Speaking of freezing avoid allowing your mixture to to so. Thanks for the advice. Will the rigidizer hold up for a while without coating it? Quote Link to comment Share on other sites More sharing options...
ForgeNub Posted March 16, 2017 Share Posted March 16, 2017 Meeco's Red Devil 610 is Rated to 3000, if you have Amazon prime its free 2 day shipping and only like 20 bucks for a half gallon, I did an extremely thin coating on my forge. The container states there is no set up or cure time on the product. I feel like its super easy to apply as it comes pre-mixed and about the consistency of peanut butter. If you use it, I just applied it with gloves on and take a scoop in your fingers apply pressure to press it into the wool or the wool will just want to ball up as you try to coat. once you get your initial coating down you can slow fire it, if you do it will bubble in the thicker spots, on my forge I just chipped the bubbled areas away and it still left a coat on the wool, cracks are easy to fill and its easy to get your hands on it, I haven't lined with ITC 100 yet so I'll do one more lining of the Meeco's heat it, rasp it to a better even surface then coat with the ITC. As is my forge gets to near white hot without the ITC in about 10-15 minutes @ 10-12.5 PSI. I'm a total newbie but I think it works great! Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted March 16, 2017 Share Posted March 16, 2017 Silica based rigidizer is colloidal; it remains suspended in water for loooooong periods. There are also colloidal alumina rgidizer, along with non-colloidal alumina rigidezer; that is all the kinds of rigidizers their are...for now. Once the rigidizer is set with flame it becomes a physical part of the ceramic blanket; if you mechanical injure the blanket, that is the only change that happens in the rigidizer afterward. Their is no hurry to get to the coating. Quote Link to comment Share on other sites More sharing options...
iamjoe Posted March 16, 2017 Author Share Posted March 16, 2017 5 hours ago, Mikey98118 said: Once the rigidizer is set with flame it becomes a physical part of the ceramic blanket; if you mechanical injure the blanket, that is the only change that happens in the rigidizer afterward. Their is no hurry to get to the coating. Thanks. Just what I needed to know. Thanks everyone. Quote Link to comment Share on other sites More sharing options...
MattR Posted March 21, 2017 Share Posted March 21, 2017 So I keep reading about the same ceramic blanket coatings everyone always suggests. However, no matter the amount about of research I do I just can't find any information regarding the material i just picked up. Maybe dinnertime here can enlighten me about how good this material might be. Unifrax Topcoat M. I went to a nice refractory supplier a few days ago, and the owner helped me pick out the materials. Also looking at all the different options for a decent base to prop on the bottom. Choosing between soft porous bricks, El cheapo fire bricks and the one I chose, silicone carbide. I hope it was a decent choice. He told me shift firebrick have a thermal conductivity of about 10 percent. Silicone carbide is about a 70%. Sorry for the long post. If you made it this far thanks. Any input is appreciated. Thanks. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted March 23, 2017 Share Posted March 23, 2017 Silicon carbide is made of silicon and carbon. Carbon is not very insulating, and silicon is downright conductive; a poor choice. Quote Link to comment Share on other sites More sharing options...
Frosty Posted March 24, 2017 Share Posted March 24, 2017 You want a lower conductivity, 70% isn't what you want! If you plan on doing any forge welding you want high alumina or a phosphate bonded refractory to resist the ability of HOT borax to dissolve silicates. High alumina castable refractories are a LOT more commonly available than phosphate and phosphate bonded ones. Cast-O-Lite 30 is a castable high alumina bubble refractory it's conductivity is good, not soft fire brick good but WAY better than 70%. check out the "Forges 101" thread we do a lot of talking about and link to good forge designs. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
MattR Posted March 24, 2017 Share Posted March 24, 2017 Lucky, I screwed up when i wrote that. The topcoat m is just a ceramic blanket coating in my forge design. He said its main job is to resist break down from alkali. I have a lining around the forge made up of two layers of 1" 2800° blanket. The stone is just a shelf for setting the metal on. I bought two cheap thin firebricks to set underneath in the front and back for the carbide stone on, so air can flow underneath. He said the carbide is high conductivity and can retain heat and heat up quick so when you put your metal back in on it, it will help heat it up a lot faster. I guess this in return keeps a higher furnace temp when opening it up. I just wonder why i haven't seen these talked about. This refractory owned family business i went to rebuilds the large plants furnaces in NY. Quote Link to comment Share on other sites More sharing options...
iamjoe Posted March 24, 2017 Author Share Posted March 24, 2017 The fumed silica I ordered should arrive in the next day or two. Most everyone agrees that is a good first step. I probably will put doors on it next. Just sliding bricks. I know I can't close it off completely since it is a venturi burner. Thanks again for all the feedback. Frosty, I'll keep all my questions in the forges 101 section from here on. A lot of good info there and it keeps it consolidated. Quote Link to comment Share on other sites More sharing options...
Frosty Posted March 24, 2017 Share Posted March 24, 2017 Matt: There are more than one thoughts about how a furnace works best. What your refractory folk are saying is perfectly true, it is the better way to construct and operate a furnace. IF it's a large commercial furnace that gets a quantity of new material put in and hot stock removed often. They need to maintain the furnace's internal temperature or: #1, the refractory will degrade quickly from the thermal cycling. #2 Fresh cold stock draws the temperature down. #3 they're cycling stock through rapidly so they need it to heat quickly. #4 Fuel isn't a problem. #5 Having a really HOT the shop is the norm for commercial forge or foundry operations. A furnace liner in a large commercial furnace is designed to be a large heat sink, think of it as a thermal battery. it stores heat so cold stock inserted is heated quickly and it doesn't draw the liner temperature down much because there is so much of it. Our home forges heat the stock the same way, it's called a "reverbratory forge" The flame heats the forge liner and the liner sheds heat into the stock via IR. This is the same as an industrial furnace. However we aren't heating a few hundred TONS an hour FAST, we're heating MAYBE a few pounds an hour, a pound or more likely a few ounces at a time. We want it fast say under 3 minutes but it's a world of difference in scale. In our circumstances, probably better called scale the need for the liner to be a heat reservoir is significantly smaller scale. Just uncoated Kaowool is more than enough heat sink to operate a forge on our scale. I did it that way for quite a while and just replaced it often because it's so fragile. A bare kaowool liner comes to high yellow heat in under a minute and I've never noticed it visibly lose color from inserting cold stock, even 1" dia. plus in a forge with an ID of 6" running on a single 3/4" burner. Applying a castable refractory inner liner, "Flame face" causes it to take about 4 minutes to come to yellow, high yellow in 5 minutes+. I've never timed how long it takes to heat cold stock but am sure it does so faster, physics is physics. A 1/2" hard flame face does a number of things but being a significant heat sink is NOT one. #1, it encapsulates the ceramic fibers so we aren't breathing them! #2, a hard flame face is just plain tougher, one missed insertion won't rip the liner out of the forge. #3 Use the right refractory and it's immune to chemical erosion from forge welding fluxes containing borax in any of it's forms. High alumina refractories are immune to HOT borax, is darned tough stuff and can be had for pretty darned reasonable online. Anyway, the folk are telling you the truth about refractories it just doesn't apply to a home scale forge, unless you're loading yours with rail cars or big fork lifts. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
MattR Posted March 24, 2017 Share Posted March 24, 2017 I agree completely I'll post a video or pictures hopefully by the end of the weekend with a running two 3/4" burner forge. Here is my burner setup that I made. The three 8 32 screws are removable which allow the complete burner assembly to be extracted to exchange tips if need be. Since the photo I pulled out the adjustable baffle plate it is not needed it burns clean from cracking open the regulator on up to 30 PSI perfectly. I also shaved down the vortex plate to be super thin and sharp to allow the cleanest air flow. The nozzle is stainless and the threads are also machine out just like the intake Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted March 24, 2017 Share Posted March 24, 2017 It would be good to see what kind of flame that burner produces; it looks like a competent design from what I can see in the photo. A heat regenerating coating on a high alumina kiln shelf may be worthwhile, or not. But such a coating on a silicon carbide kiln shelf is pretty much of a practical necessity. It will improve performance and provide a needed shield for hot borax in welding flux. I would suggest choosing Frosty's kiln wash, because of its toughness; in such a position would be a BIG plus factor. Quote Link to comment Share on other sites More sharing options...
MattR Posted March 24, 2017 Share Posted March 24, 2017 I'll definitely look into that. Thanks Quote Link to comment Share on other sites More sharing options...
iamjoe Posted March 24, 2017 Author Share Posted March 24, 2017 Here is a video of my 3/4" burner. 20170131_210723.mp4 Quote Link to comment Share on other sites More sharing options...
Frosty Posted March 24, 2017 Share Posted March 24, 2017 MY kiln wash?! The club went in and purchased a quantity of zirconium silicate from Seattle Pottery and divvied it up. I just mixed some with the Cast-O-Lite-30 refractory I use for the hard face. Anyway, I just used some of the refractory as a matrix to hold the zirconium and stick it to the forge walls. I mixed it 2pts zirconium to 1pt. CasTOlite and enough water to make a thick paint consistency. You must stir it constantly or it separates. I cringe at calling it MY kiln wash but maybe I AM to blame. It does appear to be working pretty well and it's staying stuck. Oh, wet the forge walls before applying ANY kiln wash or it'll flash dry against the forge wall and not bond properly!! Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted March 25, 2017 Share Posted March 25, 2017 Well, aw shucks; anyway you've provided the information he needs to get the kiln wash he needs to deal properly with a silicon carbide kiln shelf. The problem with these shelves is that they are meant to transfer heat; in a pottery kiln this is good. But they were never designed to be used in a forge, Quote Link to comment Share on other sites More sharing options...
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