Show us your Door Thread

[rsandler]

Looks like you should call that Franken-door =)
It does make me wonder if a "beanbag" approach would work using Nomex with perlite/vermiculite as filling... you could push it partway into the doorway and it would mold itself to the shape and still be loose enough to remove. You could use it to plug the opening and still have a wood face to give it some rigidity to block the vent landing as well.

Worth a shot--might be tough to keep it from sagging, especially if you have it relatively thick. But, as long as it stays upright enough to block the whole oven mouth, doesn't really matter how it sags. And you might not need it that thick. I think David S has pointed out on other threads that loose perlite/vermiculite is actually a better insulator than CF blanket (although the concrete versions are significantly less efficient).

Worst case, cut the stitches with a seam ripper and fill it back up with something else. Small as it is, the little bobbin I got off Amazon has enough thread for a dozen doors.

[AJH]

Looks like you should call that Franken-door =)
It does make me wonder if a "beanbag" approach would work using Nomex with perlite/vermiculite as filling... you could push it partway into the doorway and it would mold itself to the shape and still be loose enough to remove. You could use it to plug the opening and still have a wood face to give it some rigidity to block the vent landing as well.

[rsandler]

Inspired by a post I saw somewhere (I thought in this thread, but a search doesn't turn it up) of using kevlar skids to make a door easier to slide, I thought "why not make the whole door casing out of Kevlar?" I used to do fire spinning back in college (still do occasionally), and we used kevlar for the fire wicks. If you can soak it in camp fuel and light it on fire, surely it could stand up to oven heat, right? It would be a lot lighter than metal, wouldn't conduct heat, and has a little bit of give, such that it would serve as its own gasket.

After doing a bit of research, I found that if you're going to use aramid fabric for a heat resistant application, you want Nomex, rather than Kevlar--it doesn't have as high of tensile strength, but has much better heat resistance. We're stopping heat loss, not bullets, after all. I found a source online (thefeltstore.com) that sold Nomex felt for a reasonable price, and ordered a small bobbin of Nomex thread from a seller on Amazon. Total materials cost about $50 for the fabric and thread, including shipping.

My door is made of two 2" thick pieces of leftover CalSil from my oven build, with a single piece of 1/8" Nomex felt wrapped around. I cut small wedges out of the top edges of the felt to let it fold down smoothly, and sewed a pretty rough seam with a curved "upholstery" needle. I then glued a wood facade (walnut with a spar urethane finish) onto the outside with a bunch of Liquid Nails Extreme. The door sits against the reveal of my inner arch, rather than going inside.

Total weight is about 11 pounds, most of that from the insulation (the CalSil boards are 7lbs by themselves), which is pretty good for a 4" thick door, I figure.

So far the Nomex is holding out great--soot covered on the inside, of course, but no sign of degradation in the fabric or the stitches after half a dozen full pizza fires. Heat retention is fantastic--I get 425F the next morning after a quick <1hour firing for just a couple pizzas, and had over 550 the one time I added a few more logs after finishing with pizzas in expectation of baking bread.

I think there's real potential for using Nomex as door exteriors. One could probably eschew the wood facade, and just sew on heavy duty straps (leather, perhaps) if you don't mind the look. One could even embroider the outside if you had the skill (I sure don't). Although you'd need to think more carefully about sewing good seams, I also think you could essentially sew a cushion cover out of Nomex felt and stuff it with CF blanket instead of CalSil, as if it were a pillow. That would reduce the weight substantially, and the additional give would probably make a tighter seal. Just would need to make sure it's stiff enough to hold it's shape.

Thanks for looking!

[david s]

No, this is a bad idea IMO. For my first oven I thought I was being clever and made the oven mouth and door slightly conical so that the door fitted nicely. The mistake was not to account for the shrinkage on oven cooling, when placing the cooler door inside the oven mouth. The result was the door jammed so tight in the oven mouth it was extremely difficult to remove. It is far better to have the face of the door sitting against the face of the oven mouth. For the same reason, this method is superior to a hinged door.

[rsandler]

Lots of great doors on here. A question for folks--thoughts on having the door go through the entry arch (like a plug) with a small lip of something to sit against the reveal, vs the body of the door sitting against the reveal? Seems like a majority of the door builds in this thread do the plug version, but a few do the other way, and I if I follow the pictures, there are some hybrids, with most of the door outside, but a small bit going into the arch. I also saw a build thread where david s specifically recommended not doing the plug approach. My first oven had the door built plug-style, but getting that to fit snug-but-not-too-snug was a pain in the neck. Trying to think through what to do on my current build.

[david s]

Very nice job. I’d be very interested to know how it operates. Not sure of the thickness of stainless you used, but it is notorious for warping from heat. The thinner the stainless the greater the problem. This can cause sealing issues against the rebate which can negate any gains in heat retention from the insulation.

[UtahBeehiver]

Great job on repurposing SS and use of ceramic glass.

[dfhood]

Stainless pieces upcycled from junked commercial cooler, stainless rivets and handles (may need to use potholders -_-), ceramic glass, ~2.75" ceramic insulation, 5" thermometer from forno store inset into 2" hole, and probe guard on back. Would've been nice to weld this door together, but did what I could with what I had. Hoping it will help to retain heat decently, despite the amount of glass. Looking forward to using it later this month. Planning to also make a simple separate door (thin, lightweight) for easier airflow control if desired.
Door pictured is intended for retained heat baking, with visibility using a flashlight.

[Sixto]

The aluminium is only for my outer door. Aluminium does not play that nicely with heat. For insulation, encapsulated in the steel box on the inside of my wooden door, furnace blanket works really well.

Got it. thanks Mark! I'll probably do two doors, a stainless steel sheet with no insulation and a perlite/refractory cement like what David described.

[MarkJerling]

That sounds great for the Stainless or Aluminum, Thanks Mark! Any suggestions about the insulation material if I can't get calcium silicate???

The aluminium is only for my outer door. Aluminium does not play that nicely with heat. For insulation, encapsulated in the steel box on the inside of my wooden door, furnace blanket works really well.

[fox]

I use a very similar solution to David but use vermiculite board for the backing, I use vermiculite and metal for the inner door and vermiculite and wood for the outer door.
vermiculite board is used to line wood burning stoves and is readily available at associated stores.

[Sixto]

That makes perfect sense! Thank you for your detailed response David!

[david s]

Because earlier versions of the insulating panel were not really strong enough, they wore out with a fair bit of use. I had used mill board which is about as strong as calcium silicate board. The cast panels I have developed use a 4:1 mix of sand and calcium aluminate cement to a depth of around 3mm which becomes the face of the panel sitting against the oven mouth. I then immediately make up a mix of 125ml calcium aluminate cement,500 ml sand and 700 ml medium grade perlite and some AR glass fibres and some pp fibres. For added strength I also embed three 6mm round steel bars into the centre of this layer for added strength. This is enough to fill the remaining 17mm of mould thickness. On remoulding 24 hrs later I wrap the panel in plastic for a further two days.
One big advantage of calcium aluminate cement, apart from its ability to withstand higher temperatures than OPC, is that it achieves its full strength after 24 hrs, although I always give it a couple of days to be sure. It has taken me a long time to arrive at this brew because the panel can be made stronger with the addition of more cement, but that reduces its insulating capacity. The richer mix for the face that faces the heat and sits against the oven mouth does a good job of strengthening that part. A metal facing is an alternative solution, but because it is so conductive is working against you to work as an insulator. It also increases the door weight substantially and introduces a third layer of material which adds to the fabrication costs in terms of labour and materials.I have considered doubling the panel thickness but that would increase the weight, make handling the door more difficult and the door would require two handles rather than one. This modification would also increase cost of materials and labour. For folk making a one off door the extra labour and materials are probably not a factor.

[Sixto]

...My solution, which does have its drawbacks, is to use a 20mmm wooden door with a cast 20mm insulating panel bolted to it using 3/16" 316 stainless bolts, being as thin as I dared to reduce conductivity, and with the panel held away from the wooden door with high temp silicon to reduce heat travel by conductivity...

Thanks DavId!, I like the wood look and functionality also. Can you share more details about the cast insulated panel? is that a perlite/vermiculite and cement mix? If so, what ratio would be strong enough to face the fire directly, and would you recommend a leaner, more insulating mix if you had a metal layer facing the fire?

[david s]

I came at it from a different angle. I like the look of a wooden door as it's traditional for Italian ovens. But the problem is that it burns if it gets to 250C.The Italian's solution was to soak the door in a bucket of water prior to fitting it.If it charred up badly they'd just make another.
Using a highly conductive material like stainless or aluminium as a facing for the door, where you are wanting it to insulate seems counter productive.
My solution, which does have its drawbacks, is to use a 20mmm wooden door with a cast 20mm insulating panel bolted to it using 3/16" 316 stainless bolts, being as thin as I dared to reduce conductivity, and with the panel held away from the wooden door with high temp silicon to reduce heat travel by conductivity.
I've arrived at this solution mainly due to fabrication time and appearance.
The insulating panel needs to be fairly light and insulating, but at the same time durable. This is not easy because you can make it stronger but that reduces insulation value. Making it more insulating makes the panel lighter but very susceptible to wear and damage. A compromise somewhere in the middle is how I now do it.
I works pretty well, but you can't place the door after a pizza cook up and expect it to hold the heat the next day because the door will burn. Because my oven is small it's no big deal to flash it up again, but for roasting and baking with the oven below 300C, the 20mm of insulation does a fine job of both holding the heat and protecting the timber door.

The one handed operation is also a bonus with the door's total weight only 3.3kg