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For those of you who have made their ovens and used insulation, I have a simple question: What type of insulation did you use? I am in the process of putting together my PID driven oven and am not sure what insulation I should be getting and where.  (Scott Wolfe)

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I've used the MinWool-1200 in 1 1/2" thickness on two ovens. It has a 1200 degree temp range, good R value, the only problem for most not in the HVAC business is locating it. You may need to call local HVAC suppliers or look online, or call Mansville for a retailer in your area. You sure won't find it in the big box stores.

You can also use regular duct liner, available just about anywhere. It's only good to 350 degrees, but I personally don't see that as a problem for most heat treating. I took a torch to the stuff in the shop and it takes quite a bit more heat than that to make it melt - it doesn't catch fire.

I like the density and compression of these products VS fiberglass for layering in between two pieces of sheet metal. Look for mineral wool or volcanic type materials too.  (Tom Vagell)

I used 1 inch duct board that any small heating and cooling outfit will carry.  It comes in a large sheet, 4 x 10 ft if I remember, which is more than you will ever need for an oven.  It's foil faced on both sides.  (Scott Bahn)

OK, so I need to add some insulation to my heat gun oven. So what kind of temps can standard old fiberglass bats take? I figure I need to ramp this sucker up to about 375-400 degrees and then let it drop back to 350-375 when I insert the cane in the MD fixtures. So will fiberglass survive this or do I need to look for the super hi-temp ($$$) stuff.  (Larry Puckett)

I went to the plumber supply and purchased high temp pipe insulation. It's that stuff like is put around steam pipes. It comes in 4' sections. You can also get an end cap. I purchased the next size down and removed some of the inside and it fit snug. If you get the correct size it will be a bit loose. The pink household insulation that we have all seen blowing around construction sites is not rated for that kind of heat.  (Timothy Troester)

I agree that steam line insulation is a good choice, but there are many types of steam line insulation along other options.   Go to McMaster-Carr on-line and look up insulation.  The search will show several options and the operating temperature range is clearly posted.    I have experience with most of the insulations listed along with others.  I chose 2” mineral wool for my oven and it is more than adequate.    It is not a bad idea to review the MSDS prior to purchasing industrial insulation.  (Ray Taylor)

It kind of depends on what kind of pipe you used for the oven in the first place.  If it's single wall, the outside will get to about the same temp as the inside pretty quickly, and probably needs the high temp. stuff.  Double wall not so much.  If you have a digital thermometer, or better one of the infrared ones that don't require contact you could tell how hot the outside is and go from there.  Fiberglass itself  won't burn,  but if the paper gets too hot...  OTOH, "Fahrenheit 451" was supposed to be based on the temperature at which paper burns.  I sure wouldn't put the paper side in on any kind of heat gun oven.  (Neil Savage)

I used regular fiberglass batting from the hardware store.  No, not the stuff with paper on it and the color is yellow.  I think it is often used for heating ducts and I happened to have some lying around when I decided to insulate my heat gun oven.  I used two layers and then enclosed them in metal duct-tube that is 2" larger in diameter than the larger (outer)( tube of the oven.  I provided even standoff space for the insulation between the outermost tube and the outer oven tube with a number of 1 1/4" sheet metal screws that are screwed through the outer tube and have their points up against  (but not through) the outer oven tube.

I heat the oven often to 350º F, but very seldom above 360º F.  At first the fiberglass batting gave off a little smell.  There were no flames and I have used the oven a lot since insulating it without any problems. (Tim Anderson)

This is exactly what I am planning to do. I already have the basic unit built with a 3” pipe inside a 6” pipe, and I am planning on nesting that inside an 8” pipe with the insulation packed between them. I found a web site with properties of various insulation materials and it says that plain fiberglass can easily take 1000 degrees, so I guess I’ll give that a shot.  (Larry Puckett)

You may already know this but some may not. It's difficult to slide the outside pipe over the insulation and the inter pipe. An easy way to do this is to open the seam on the outer pipe slightly and place the outer pipe over the insulation and inter pipe. Place a hose clamp or multiple hose clamps strung together if you don’t have one long enough around the outer pipe and tighten the clamps, usually 3 clamps, one on each end and one in the middle to pull the pipe together till the seam "hooks" together. Easy & simple.  (Don Anderson)

When installing  the insulation, should it be compressed as much as possible or just laid on as it comes?  (Roland Cote)

Using two layers, I compressed the insulation.  An individual layer of what I used is about 1" thick.  Don's suggestion is a good one.  I did something similar and a few, well-chosen, colorful words also helped.  My holes for thermometers are larger in the outermost tube so I can easily see the smaller holes into the oven.  (Tim Anderson)

If you use fiberglass or glass wool, it should be uncompressed.  It works by trapping air in the space between the fibers, air being a poor conductor.  (Neil Savage)

If you are going to compress the insulation, you'd be better off to leave it out. It's the trapped air in the fiberglass that does the job. The glass fibers just keep the air from moving.  (Tom Kurtis)

I use the pink stuff. I removed the paper when I built my direct heat toaster oven. I run that at 195C. I had a heat gun oven before this one that was insulated with the pink stuff, with the paper still on. One afternoon I got distracted with the gun on high and it got hot enough to melt solder. The insulation survived. I had to go to several stores to find the real glass insulation. A lot of the current 'no itch' stuff is a lot more flammable.  (Larry Lohkamp)

You need to use the boiler grade insulation, like the rock wool stuff that was mentioned the other day, or the ceramic wool insulation like I used in my oven.  Either variety can be had at an industrial insulation supplier.  It's not that expensive.  Itchy as hell, but not terribly expensive...  (Mark Wendt)

My experience has been that the insulation is not that critical.  In fact, my oven was way over built to the effect that, with a less precise heat gun, the temp rose to workable quickly and then kept rapidly soaring becoming difficult to control.  I toyed with the idea of putting a vent in the other end but the problem was solved when I got an infinitely controllable heat gun.  My advice is don't worry over much about the external insulation - just enough to keep the outer shell manageable.  This ain't a jet engine.  (Though mine looks like one) ;^)  (Darrol Groth)

I insulated mine because the temperatures in my shop were in the low 40s when I first tried it.  My heat gun is a very good one, but I had to use a propane torch on the outside of the oven to get it up to temperature.  That seemed like a stupid thing to continue with.  (Tim Anderson)

I built my heat gun oven using two lengths of circular metal duct with a reducer on either end of the inner tube which pokes through an end cap riveted to the larger external tube, I thought about filling the void with fiberglass but thought I wouldn't get a good fit into the complete space so I filled the void with vermiculite which is a great insulator and easy to pour into the upturned end of the oven, it also acts as a really good support for the inner tube.  (Nick Brett)

I am in the process of testing my heat gun oven based exactly on Frank Neunemann's design.  It is hanging horizontally, without insulation, and the heat gun is a two speed Wagner HT-100.  The heat gun on the high setting (1,000 degrees) after 15 minutes seemed to stabilize at 345 degrees with approximately a 20 degree difference between the end with the heat in contrast to the other side.  I have some of Harry's heat treating fixtures so it seems that insulation will be necessary.  What type of insulation (plain old fiberglass, high temp pipe grade, etc.)?  Does Home Depot or Lowes sell anything that will work?  (Ron Delesky)

On my heat gun oven I used the foil backed heating duct insulation from Home Depot. I put it on with, of all things, duct tape.

My oven uses two five foot lengths of round heating duct, 2" and 5" diameter, for inner and outer tubes. The steel heating duct is cheaper than galvanized stove pipe. If your stove is over 5" in diameter I'm not sure if the heating duct insulation is wide enough to wrap around in a single piece as I could do.

Initially I had over a 30 degree temperature differential between the heat gun end the other end of the oven. I added a hardware cloth (left over from making a rack for the bamboo strips inside the 2" section) tube about 2 feet long to the heat gun end and wrapped it with aluminum foil. This made the middle of the oven about 10 to 15 degrees hotter than the ends. I guessed at a couple hole locations that I made in the aluminum foil wrapped on the hardware cloth. The steady state temperature differential was then about 5 degrees hotter at the heat gun end so I quit and declared the oven as finished. (Joe Hudock)

We had a thread on here recently where I asked the same question. After a bunch of responses and some online research I decided to just use plain old fiberglass since it softens at about 1500 degrees and melts at 2000 degrees. Since my oven is made using a 6" dia stove pipe I decided to wrap 1" of insulation around it and insert it inside an 8" diameter stove pipe using metal brackets at each end to keep it centered. As soon as I get it finished I'll let you know how it works.  (Larry Puckett)

This is basically how I did mine and it works well. Maybe not as much as the nicer commercially made ovens but this is what I have to deal with.  You can always flip the fixtures half way through if you are overly concerned.  (Greg Reeves)

I used regular Fiberglass insulation on my Heat Gun Oven for 4 years. The problem is that the stuff STINKS when it gets hot.  I don't know what gas it's putting out but I don't like the smell. Finally switched to some rock wool insulation from McMaster-Carr. Problem is that it comes in sheet form and is a bit stiff.  I had to cut longitudinal slits to get it to conform to the shape of the tube. There's probably something better out there.  (Larry Swearingen)

Why don't y'all just use boiler wrap.  You know, the stuff that's intended to take high heat?  The stuff that's flexible?  The stuff that's designed for all this? (Mark Wendt)

I used the fiberglass insulation which is sold for wrapping heating ducts.  It is yellow and has no paper attached.  It produced only a slight odor for the first two times I fired up the oven.  After that, no smell other than the nice one of bamboo baking.  (Tim Anderson)

Amazing how good the stuff that's designed to do this kinda stuff works, eh?  (Mark Wendt)

Hmm, could we not say the same about many things? For instance:

If you are searching for duct insulation that works well, here's a suggestion. Carefully measure the surface to be insulated. If it's round, convert that to flat dimensions. Now call your local sheet metal contractor, or even a good HVAC man. Tell him you want some 1" duct insulation, the black stuff. Give him the measurements, and go pick it up the next day. Wrap the insulation around your goofy shaped oven, and secure with foil tape. Voila! Insulated oven. I've made 14 ovens in 2010 so am fairly experienced at this stuff.  (Harry Boyd)

Yup.  I'm all for innovation (hence the CNC machinery and tools and...) but sometimes you just gotta use a screwdriver as a screwdriver, a hammer as a hammer, and boiler wrap, or ceramic based oven insulation as oven insulation.

There is good and cheap though, it's part of the Venn Diagram, where you see Fast, Good, and Cheap each as one side of the triangle.

You can pick only two though.  (Mark Wendt)

You make me smile.  I have the same opinion, and often say it.  As a chemist in my past years, I have spent, weeks or years perfecting a product's performance and hate to see a great product misused and then dissed.

Also your minor typo  "If yous are searching..."  made me smile as it reminded me of when my mother (bless her soul) was teaching, a young girl addressed the class and said "yous"  my mother corrected her to say "you" and the girl said "Yeah I but I was speaking to the whole class."  (Dave Burley)

I am planning to build a heat gun rod oven this evening and I am curious about insulation. I will be using stove pipe as heating ducts can only be purchased locally by licensed hvac contractors. My question is, can I wrap the stove pipe with fiberglass insulation or will it need to be a special type of insulation? Thanks for the help. (John Smith)

Try to get in touch with Tim Abbot in PA.  He demoed a really neat oven at the Canadian Cane gathering a couple of years ago.  I don't have any contact info on him. (John Long)

I would build it and test it first to determine if you need insulation.   Much will depend on the quality of your heat gun.  I use a Steinel.  The oven heats up in 15-20 minutes and it holds heat quite well without insulation. (Alan Boehm)

My purpose for the insulation was not to hold in the heat, but to keep the outer surface from being too hot to touch. (John Smith)

I would recommend that you wrap it in a 3" fiberglass bat just for that reason.  It will also help it retain heat, and so, use less power. My heat gun oven is a wooden box made with 1"x6"x6' cedar boards.  It doesn't get too hot, but it also leaks a lot of heat.  It has been adequate, but I think I can do better. (Paul Gruver)

You will find the insulation keeps enough heat in to make it work. I had one for years and it would only get to the right temp was when I insulated it.  (Gordon Koppin)

This link provides temperature ratings for various insulation materials.  However, I don't know if their ratings are reliable.  (Ron Delesky)

I think most any kind of fiberglass insulation will work. I just got the cheapest stuff I could find at Home Depot. Its an inch or so thick with a foil face. I have the foil facing out.

I used to have the insulation wrapped with a few turns of foil tape to hold it on but the glue gave out on the tape after a few years so now I use (but what else) plain old duct tape, the cheap gray stuff. It also goes after a few years but I have plenty on hand since its handy for other stuff like holding my belt sander steady when I use it for a surface grinder for precision metal work.

To augment the insulation for heat treating I drape some old quilts and bedspreads, that I normally use for painting drop cloths, over the heat gun oven when its cold in the garage. Without them I can't get the oven to 375 degrees when its -10 or colder in the garage. In the spring, fall or summer I don't need the quilts for heat treating.

When I built my heat gun oven it did require some 'tuning' to get a more or less uniform temperature over its length. If you have that problem and care to hear from me about that let me know.

Where do you live that you can't by heating duct without a license? You must have a Home Depot. I live at the edge of the earth, well almost, close to the Canadian border, and we have a Home Depot. Here is a link for one of the pieces of heating duct I used. (Joe Hudock)

I would check the heat rating on the fiberglass insulation not all of it will be sufficient.  If memory serves me, normal fiberglass wall insulation has a melting point of approximately 250 degrees, (heat treating happens at a much higher temp).  The outside wall of the pipe will be nominally the same temp as the inside air temp which will be much higher than 250 degrees and thus an insulation with a higher melting point should be used.  I would recommend using a "water heater blanket" which does have a higher heat rating and comes with a foil back.  Further, to tape the blanket I would recommend using high heat tape.  All of these can generally be found at a big box home store. (Mark Polistina)

It was a while back but I think the insulation I got was for insulating heating ducts and it does have a foil back. Anyhow it was right near the heat duct pipe there at Home Depot. Also the silver tape was the high temperature stuff (again, its close to the heat duct pipe at Home Depot) and it worked no better than the plain vanilla duct tape. My theory is that the outside of the insulation is nowhere as hot, like just warm, as the inside by the pipe and the tape problem is not high temperature but low, like 10 or 20 below, or maybe its thermal cycling from 10 or 20 below to a balmy 40 above. But that's just my guess.  (Joe Hudock)

I did much the same thing but one step farther.  My oven (Frank Nuenemann design) wouldn't get up to 350 f so I added 1inch figerglass with foil face to the outside.  After several failed attempts to find something to hold the insulation in place I just added one more section of duct over the outside.  So I now have a 3" inner pipe, 6" outer pipe, 1" of fiberglass, and an 8" cover pipe. The standard stove pipe is snap together and you can wrap it over the insulation and snap it together with the help of a couple of band clamps. (Rick Hodges)

I did the same thing but used it horizontally with a wire mesh in the 3" pipe to sit the bamboo on. Very easy to use and the heat was pretty consistent. (Gordon Koppin)

I assume you are trying to keep the heat inside the chamber consistent. The problem with fiberglass building insulation is that it’s too thick. Unless you make the interstitial space between the outer wall of the duct and the sleeve the same thickness as the insulation, say 3 ½”, you will have to compress the insulation so much that it loses most of it’s R-value. And you shouldn’t use the paper backed insulation, because the tar like adhesive melts. I suppose you may find thinner fiberglass with no backing, but I’ve never seen it. If you are only wrapping around the outside of a pipe and zip tying it in place with no outside sleeve ducting, none of the above matters anyway.

The best product I have found is duct liner. I’ve used it in 3 ovens. It is a black, highly compressed insulation used inside commercial supply/return rectangular ducting. It is commonly 1” thick. You probably won’t find it at the big box stores, it is typically only sold by HVAC wholesalers. Your best bet is to find a local HVAC contractor with a fabrication shop who does commercial work. The stuff is cheap, and the fab process produces a fair amount of waste. You could probably get the scraps for free.

The only drawback I can see is the ability to roll duct liner on round duct. It is a little rigid, I’m guessing if you score it a little with a razor knife you could roll it easier. I have only made rectangular ovens, so I haven’t face this problem. Like I said, if you aren’t doing a sleeve (larger diameter pipe around smaller to create a space for the insulation for durability and maximum protection against heat loss) you can use any type of insulation readily available.  (Tom Vagell)

If as Tom suggested you are planning to install the insulation in a double walled space, then you can buy the loose fill stuff they blow into attics and walls and just pour it into the cavity. Trying to insert batts or flat sheets of insulation into a cavity is a PITA. (Larry Puckett)

Fiberglass has a much higher melting point than you will ever achieve with a heat gun oven. I would recommend against using paper or plastic faced insulation. See if you can find foil faced or use unfaced and wrap it with heavy duty foil to protect it.  (Larry Puckett)