Bamboo Tips - Tips Area
Tool Building - Ovens - Heat Sinks

< Home < Tips Area < Tool Building < Ovens < Heat Sinks

Does anybody have any experience with installing some sort of a "heat sink" in a mica strip oven in order to mitigate the temp variation?  I have been considering placing a 1/8" thick aluminum channel with holes drilled in it on the hardware cloth of my oven, but won't do it if it's not worth the effort.  I remember talking w/ John Zimny a few years back about installing fire brick in an oven.  I'm not sure if he did it or not.  (David Van Burgel)

Hate to be a nay-sayer, but I have done exactly what you suggest and found it had little if any affect.  I completely covered the mica strip element with some aluminum scraps left over from a window project at the church.  What has helped me is using forced air.  (Harry Boyd)

Yup, the only way to really avoid hot spots is to get a convection oven.  The heat is in the air, rather than being a radiant heat source.  (Mark Wendt)

If I were going to try it, I think I'd put a goodly piece of metal in the cold area.  Once it got hot, it should help even out the temperature. However, as Harry says, forced air should do the job at least as well and probably better.  That's how the heat gun ovens work.  (Neil Savage)

Speaking of forced air, I built the heat gun oven an it works perfectly.  I use a $10.00 digital thermometer I bought at the local grocery store and a $20.00 Wagner heat gun with two settings.  The temp is easily controlled by switching the heat gun between the high and low settings.

The oven is cheap and easy to build.  the only mod. I made was to insulate the oven with fiberglass and slide a large cylinder oven the whole thing.  I used it last night in my garage and the temp in the garage was in the high 20 degrees F.  It worked like a charm!  Note: next time I am going to use it in the house.  It is just too cold in the garage in Colorado this year.

Cheap, easy, no hot spots. 

I have used the mica oven and had to keep flipping the cane to get an near even heat treating.  The heat gun oven removes all frustration I encountered with the mica oven.  (David Gerich)

Mine is built with the strip embedded in an iron u-channel, and it still has hot spots. I'm pondering a fan setup to keep the air moving as a way to even it out. Let me know if you come up with anything good.  (Kevin Little)

Adding air movement MAY solve, or exacerbate, the problem.  If you try to push more air through your oven your oven may end up with turbulence that prevents even flow and creates even greater hot spots.  (Ralph Tuttle)

Yup, you do have to smoothen out the rough spots and corners in the oven to get good air flow.  Separating the heater element chamber from the rod section chamber will keep the radiant heat from getting to the rod sections, leaving just the convection air to heat your cane.  (Mark Wendt)

I put a layer of brick in my oven, and it seems to work great. I have only a few degrees difference between front and back, although the oven takes about 15 minutes longer (from cold) to reach my settings.

I  built  a  shelf  out  of  strong  hardware  cloth -- merely bent 90-degrees downward along both sides to form two, full-length "legs." This just slips into the oven and its surface is about 2" above the mica strip -- bricks laid on top of that.

The bricks themselves are only the 1/2" veneer pavers (not actually fire brick), but they seem to be perfectly adequate for the purpose. I allowed 1/2" open space along the length of both sides for a little free circulation, but otherwise the layer of brick is continuous. A full layer of brick (even the 1/2") is kinda heavy, so I put each row in place on the shelf as as I slipped it into the oven -- then, pushed the shelf in a little farther.

You'll need to mess around a little to lay things out according to your own dimensions, but there's certainly nothing complicated, chancy or expensive about the "tweak."  (Bill Harms)

I have a mica strip heater with a hotspot in it as well.  I decided not to put a heat sink in it because what I do is let the oven heat up for a half an hour, then put in my bound up strips.  I cook them for 7-8 minutes at 350 degrees, then open the door and flip them end to end, close the door and cook them for 7-8 minutes more, I take my time when I flip them as well so the oven does loose some heat.  My hotspot is on the door end and when I open it up for the first time and close it, it seems as though the oven evens back out for the rest of the process after it has warmed up.  My strips seem to come out with a nice even color and there does not seem to be any unevenness because of the "hotspot".

With such a small oven compartment, a heat sink will not do much good when the mica strip heats back up when the temp falls and the fact that the bamboo is pretty close to the mica strip anyway.  The short time that I have the strips in the oven doesn't effect them.  Guys that cook longer at a high temp will run into discoloration though.

I got hung up on the temperature difference when I first built mine but realized it didn't matter in the  end for me.   (Scott Bahn)

I tried several different heat sink ideas.  None worked.  But I didn't try Bill's brick idea.  That may be the ticket.  I modified my Cattanach style oven to be a combination of convection and radiant heat.  That fixed the hot spot problem and kept all the heat inside the box (no circulating outside the box through a blower...the blower is inside the box).  There are pictures on the contraptions page.  (David Bolin)

What I did was to line the floor of the oven with the fire bricks (strip under the bricks) that you use to place a wood burning stove on. I then heat the oven for no less that 30 minutes at the desired heat. I will open the oven for 10 minutes before I turn it off so air and the heat can move around the oven. I feel that helps to reduce the hot spots. Then, I turn the oven off it will stay hot at the temperature within 10 to 15 degrees for close to 45 minutes. I guess it works like a pizza oven. It is the bricks that retain the heat and hold the temperature and not the mica strips that tend to give a very uneven heat displacement. I am not a control freak when it comes to these sorts of things. I think that it is hard to control things that grow with so many variations anyway size of the fibers wet growth years dry growth years would a windy season make stronger denser fibers that sort of thing. I do not get any more scorch marks on my cane splines anyway.  (Wayne Daley)

The question to answer first:  Is the temp variation due to your controller hysteresis?  If your controller turns off at 350F and comes back on at 325F you're stuck with that variation.  If you use a controller with a smaller hysteresis, say 5F, but have a variation of 25F, then the issue is that the air movement is inadequate.  (Al Baldauski)