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About D.Rotblatt

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  1. D.Rotblatt

    3D printed plastic burner experiments (photo heavy)

    Agree with John. Plaster of Paris degrades at a very low temperature. You need to use an investment for casting. Do a search for "molding investment" on amazon. I've done more shell casting, but did some investment casting years ago and that's the type you should get. For DIY investment, as I recall it was equal mix of 1/3 casting plaster, 1/3 sand, 1/3 grog (I read that powdered clay available at pottery supplies would work, I think powdered old soft firebrick would probably work too). The Plaster is a binder, the sand is a refractory, and they powdered clay/grog is a modifier and strengthen the mix. Give that a try, it will work better then then plaster of paris alone.
  2. D.Rotblatt

    Ribbon Burner Backfire Question

    OK. First plugged the lower row of holes. Burner was not as stable as it was before. Unplugged the outer two holes on the lower row, and either I got better at judging the air/gas mix or it was more stable. Either way, worked well with 11 holes. Got an even 1550F with a reducing flame for 10 minutes or so - no backfire, but I'll have to do a longer test later. Like an hour or so. I then turned it up. Damper opened 1/4, fan wide open and it will get to welding temps easy I think. I'm now cleaning and rearranging the studio to make more room, so I'll try some welds in a week or two. Problem Solved!!! Either plug up some holes or run a very reducing atmosphere (with doors open). Thanks all!
  3. D.Rotblatt

    Ribbon Burner Backfire Question

    Ill try it today and report back!
  4. D.Rotblatt

    Ribbon Burner Backfire Question

    Thanks Swedefiddle, I'll play with it in the next few days. I like the idea of plugging some holes and seeing what that does. It's really a no-brainer, but since the idea didn't even drift by in the back of my mind, what does that make me???? Was focusing on making a wheeled cart for the forge today (and cleaning....endless cleaning). Ideally a molten salt bath would be the way to go for HT...but I don't do enough to warrant that.
  5. D.Rotblatt

    Advice : Sunlar Electric Blacksmith Forge Blower

    The thread is a little old, but for anyone interested I happened to purchase one and it works fine. I find it noisy though, but I have nothing to compare it to. Really too much air for my ribbon burner (19 crayon sized holes, 2.5" pipe from blower to burner). I'm looking for something quieter, or maybe just put a box over it. Can't really use a variable speed switch, cause when my compressor kicks on the fan slows down if not at full power - big flames billowing out of the forge mouth, lots of fun!
  6. D.Rotblatt

    Ribbon Burner Backfire Question

    Shrike - good thoughts too. Would love a simpler fix then building two burners, though I'll keep that in mind for future builds. Perhaps the same plenum with a divider lengthwise and two intakes - so the top and bottom row(s) can be turned on independently. Fairly easy build. The plenum is not getting hot, it's the actual refractory where the holes are that's in the forge. The face gets hot, and because the gas is set to such a low volume, it is burning back into the holes - it's not a single backfire, but a phlegmy whistle (don't know how else to describe it).
  7. D.Rotblatt

    Ribbon Burner Backfire Question

    Thanks for all the replies! Buzzkill and Mikey; Excellent thoughts! Smaller burner/holes or less holes. The easiest is to plug up some holes - a little ceramic wool in a few of the holes. I'll give that a try and see what happens. As it is I have much to much pressure from the fan, so back pressure will not be a problem. Timgunn; nice discussion of the problem. I already tried a richer mixture this morning (I always use a pyrometer) and got a steady 1550F +/- 10 with a much more even heat inside the forge. I have yet to see if this will work on a long burn. I've used the rich mixture technique on my previous forge many times. My studio has a 6.5' tall 4' wide window next to the forge and an 8' wide sliding door across from it - plus a ceiling fan. Plenty of cross draft = no CO poisoning. I really wanted a dual purpose forge, it's not the money, it's the space, I just have too much stuff. Want to do fluxless forge welding and HT in the same forge (been playing with it). If not I'm modifying the forge now to take a removable kiln shelf. The shell of this forge is a small helium tank I added about 6" length to, 1" of Kaowool, lined with Zircon heat "reflector" about 1/16" thick. So the inside is 7.5" diameter and 12" long with a flat bottom. I should be able to HT a knife up to 16" long or so. For swords I have a different kiln. I also have an electric kiln with DIY PID controller, It's also about 12" deep and wide (old ceramic kiln I got for a song). I use it for HT on stainless knives, but there is a depth issue and I can't get a reducing atmosphere unless I modify it further to take an inert gas intake. In regards to a second forge just for welding; if I really get into doing a lot more forge welding, I'll build a vertical forge - just cause I haven't ever used one and I love to experiment. I have a whole roll of Ceramic wool, some old helium tanks for shells, and several Mikey burners I built years ago (I think one of them is a 1.25" burner....that would be more then enough).
  8. D.Rotblatt

    Ribbon Burner Backfire Question

    I've built my first forced air ribbon burner and put it in a new forge. It runs beautifully...except one thing. I was hoping I could run it low enough to get an even 1550F or so temp in the forge for heat treating. When I run it low, maybe 1 lb pressure (the jet is three .052" holes), fan closed up, and gate open only 1/8" and a slightly reducing flame it holds a nice heat treating temp (if a little high), but after a 10 minutes or so it backfires (the flame running back into the burner), I turn it up a little bit and it runs for awhile and then it backfires again, I turn it up....etc. In looking for answers, I found one person that said that ribbon burners do that, they backfire after awhile and you have to turn them up. In all my researches before the build I never found mention of that happening. Is this a common problem with ribbon burners? Is there something in the design? Any thoughts???? The burner is a standard build; 19 holes, 2.5" pipe leading from the fan to the burner. I'll post a pic:
  9. D.Rotblatt

    Forges 101

    An update on the Zircon/Colloidal silica eggshell lining for my forge. To recap: The shell is a small helium tank 9.5" in diameter with an added 6" in length, inside is 1" of ceramic fiber, rigidized with fused silica and water, then coated 3 or 4 times with a mix of Zircon and Colloidal Silica (as discussed on the page before this). On the bottom is a soft firebrick (K26 I believe), the surface is also coated with zircon/colloidal mix. I am considering cutting the brick 1/2" lower, and putting 3/8 " ceramic media from my tumbler on it so the bottom of the metal warms, and so I can brush it out and put in a kiln shelf if I want to use flux. I've been playing with fluxes welds - I'll see if that works in the forge well. This coating is basically what I've used this before with the following changes. The wool was rigidized first with the fumed silica, and I applies more coats of the zircon bringing it to around 1/16" thick. I must say, having rigidized the wool first with the fused silica made it much easier to apply even coats of zircon. Using a K type pyrometer; the forge gets up to forging heat (1600-1800F) in 3 minutes and starts to stabilize, and after about 5 minutes more is pretty stable in temperature. I brought it up to 2350F and it seems happy as pie, that's probably hotter then I need to forge weld. I had actually lined this forge first with 1/4-1/2" of mizzou refractory and fired it up, but it took so long to get to heat (it too over 20 minutes just to get to forging heat) that I ripped it out and relined it using my old eggshell technique. Same burner, 1/10th the heating time. Here's a pic of the forge:
  10. Ditto Mikey's post....assuming you have the gas regulated (at least with a ball valve). Is it in the forge, or are you running it in open air? If in open air, it may not be able to hold the flame. Mine worked poorly outside the forge, but inside, with some back pressure, it works perfectly.
  11. D.Rotblatt

    Forges 101

    Curtis, if you ever head down to Salt Lake city, there is a Harbison Walker location there. Give them a call. Salt Lake City, UT GSC 4521 West 1980 South Suite 503 Salt Lake City, UT 84104-4719 xxxx-xxx-xxxx
  12. D.Rotblatt

    New Forge: Lining Questions

    Thank you Frosty! I've been using Reil burners for decades, and never had them backfire when shutting off. Nor do my Mikey burners. I too have some burnout kilns where the outside shell is just 1/4" hardware cloth with 1" of kaowool. Used them for burning out ceramic shells, and have repurposed them as upright heat treat forges for hardening swords. The Zircon/Colloidal silica binder shell is fine for being just bumped. Even if it does crack or is punctured, it's easy to paint a patch on...only a few minutes, no drying time, but paint it on cool and fire the puppy up! ****I've moved the conversation to the Forges 101. Glen just told me to cut and paste it. We can move all this over there.
  13. D.Rotblatt

    Forges 101

    Mikey - I have no dog in this race! I just want to find out what works, and what works for our situation - so I hope my questions/statement didn't come off combative. Just curious and hoping to rectify a lack of knowledge. BTW: My 3000+ degree numbers are just a best guess based on melting points of the ingredients online - not any real world testing. Speaking of real world testing. Since I was putting the face on my forge today so I thought I'd try some mixes of Fused Silica against Colloidal Silica binder on some scrap pieces of ceramic fiber. RIGIDIZING The Fused Silica solution (FS) didn't soak into the fiber deeply, it stayed on the top unless the fiber was wet first. Even then it tended to stay on the surface. The Adbond II quickly soaked into the fiber quicker than water. Unfortunately when heated to red heat the Adbond II soaked fiber shrunk, the surface where it got hot turned into a solid mass. The FS formed the expected hardened layer on the surface. Another piece of fiber with only the surface 1/8" wetted with the Adbond II did rigidize fairly well. In summation, the FS solution works much better as a rigidizer, Adbond II can work if applied carefully, but if you use too much it will destroy your ceramic fiber. Adbond II is not recommended. ZIRCON/FUSED SILICA VS ZIRCON/ADBOND II A slurry of Zircon and Fused Silica was applied to a scrap of rigidized dampened ceramic fiber quickly dried in the dragons breath of the forge then put inside and brought up to red heat. It seemed to for a nice layer bonded to the surface of the fiber. I then added more Zircon to the slurry until it was the thickness of latex paint. A thick coat was applied to the surface of the fiber to make a thick second coat. This was dried the same and heated to red heat. The surface cracked (like mud) and flaked off when scraped gently. The same treatment was used for the Zircon/Adbond II mix. The second coat did not crack or come off. This was expected, since that is exactly what it is designed for when making shell molds. I even added a third coat ending up with maybe .030 or .040 thickness - like a thick egg shell. It was surprisingly strong, but a good tap with an 1/8" rod broke it. I have tested it in the past vs. flux and it is inert to flux...unless there is a crack. I went ahead and finished my forge with the FS for rigidizing, and the Zircon/Adbond II for the hardshell/emittive layer. Working on rigidized ceramic fiber made it really easy to apply the Zircon solution. I just painted it on. Fired the forge for a few seconds at a time until dry, then brought up to red heat. Let it cool (about 2-3 minutes), then applied another coat. Took me about 1 hour to face the lining. This is a really fine hard shell for surfacing the ceramic fiber, but Adbond II or any ceramic shell binder is really sold only to industry - meaning the smallest amount I've seen is 5 gal. I think I used a no more then a cup of Adbond II to do my forge (7.5" ID x 13" deep). Remet has a division for artists, so someone who is interested may want to call and talk to them and see if they will sell small amounts.
  14. D.Rotblatt

    Forges 101

    Mikey. You mentioned that the Zircon/Colloidal silica mix would not be as good at high temp as the Zircon/bentonite mix. This made me curious, so I researched it a bit. From what I can find, the colloidal silica binder is Silica Dioxide in suspension with other stuff. Silica Dioxide has a melting point upwards of 3100 degrees F. Bentonite melts at around 2200 degrees F. Seems to me that the colloidal silica binder would hold up better at high temps. It's made to bind a ceramic shell for casting steel and high temp alloys. A thought: Fumed silica is also Silica Dioxide. Since Colloidal Silica binder is expensive and only sold in 5 Gal minimum, I'll try using some fused silica and water as the binder for Zircon and see how that compares to the binder I have. -Dan
  15. D.Rotblatt

    Forges 101

    Posted this on a different thread, and Mikey suggested that I transfer the information to this thread. In a nutshell we discuss a different coating for ceramic fiber liner using Zircon and a Colloidal silica thats used in making shell molds (the brand I happen to have is Adbond II from Remet). The result is a reflective (or emissive) eggshell thick Zircon layer bonded to the ceramic fiber. ---------- I've been building forges and furnaces since the 1980's. Here's one I designed and posted several decades ago: http://www.rotblattsculpture.com/Articles/buildingabronzec.html. I've been using Reil burners and built Mikey burners as well. Now I thought I'd build a ribbon burner (or multi burner?) with a gun type delivery. I'll post some pics later. Anywho....I've been reading on how you line forges. I've done mine different. In the old days, I just used ceramic wool. When the dangers of the fibers and the wonders of the ITC stuff got publicized, I started to coat the fiber with a straight Zircon and Colloidal silica for shell casting. This was back around 10 years ago and I was teaching Art Foundry Casting at Cal State University Long Beach and got a sample of Zircon from Remet (a foundry supplier). It formed a good paper thin coating on the ceramic fiber. Heated up instantly, and stabilized the wool. I used to do a lot of shell mold casting. The colloidal silica is the binder that is used for building the layers. In shell casting, silica flour is mixed with the colloidal silica. The mold is dipped in the slurry then sprinkled with crushed silica - first layers with fine, then medium, then course. If you are casting iron, steel or a higher temperature material then bronze (I did bronze), then you use zircon flour instead of silica flour so it will take the heat. The colloidal silica is a premix that comes in 5 gallon containers. It looks like a milky water, a little thicker than water (could just be fumed silica in water, but I have no idea). The type I use is called Adbond II, and I got it from Remet. What I used to do is dab it onto wet ceramic wool with a disposable brush then just heat cure (never had the patience to just let it dry). Thickness and feel is like an eggshell (just not so smooth). One or two layers was all I use, basically to bind the outer layers so I won't be breathing in ceramic wool particles and I thought it would reflect (though now I find it's emitive...which I just found out by reading on this forum, thank you very much!). I figured since it was reflecting, a thin layer was all I needed. Seemed to work well, surface got brighter, wool was stabilized, formed a hard eggshell layer. I value a forge that heats up quick, and cools down quick. The only advantage I see of a slow cooling forge is for annealing, but if I want to do that I have an oven. A thicker heat sink liner is stronger so it holds up to more abuse, but will take a longer time to get to heat (thus use more gas). I imagine it would also act as a storage for the heat, so if a cool piece of metal is put against it it would transfer some of it's energy to the metal (but that's an argument for a denser floor rather than a dense layer of liner). The way I used to explain the advantages and disadvantages of ceramic wool vs a cast liner for furnaces is that if you are doing only one pour at a time, ceramic fiber is more efficient since it heats up quickly, but if you are doing a number of pours in a row, a cast liner is better as it holds the heat and you don't have to heat it up as much. As you say, it's really just a matter of opinion. But I think I'm starting to babble....I'll leave it at that for now. -Dan