using aluminum foil over kiln lid to reduce radiant heat loss.... could it?

[Christiane77]

Well the title says it all...  i tried a piece of foil on the top and the difference in temperature felt with my hand is impressive... i am tempted to cover the whole lid... the brick underneath seems hotter too.   I am guessing there is perhaps a reason not to do that, what do you think? 

[neilestrick]

I don't think it would have any effect. If it's on there for a while it's just going to absorb and radiate the heat of the bricks, not actually increase the insulation factor. If there was a gap between the foil and the bricks it would reflect some of the heat, but that wouldn't necessarily help to make the kiln more efficient, rather just keep the heat from radiating to surfaces above the kiln. In direct contact with the brick, though, it's just going to transfer the heat right to the metal.

@Bill Kielb have you used your laser pyrometer to compare the temperature difference between bricks and the metal banding on electric kilns?

[Bill Kielb]

1 hour ago, Christiane77 said:

what do you think? 

It will have an effect as the radiant component which will be reradiated back to the brick. This is measurable and something refractory coatings are good at as they get installed on the inside surface where their effect is more significant. It may cause the top of your kiln to grow and move more so be careful. Folks who add insulation to the top of their kiln often complain about the lid warping. It likely will not have an effect on the overall conductivity or R value though  but likely should provide a measurable improvement. Most of the heat in the kiln ends up to be radiant after about 1000 degrees, conduction and convection fall off rapidly.

[liambesaw]

I put ceramic blanket on the top of my lid and it caused a big crack in the middle, wouldn't recommend it lol

[Bill Kielb]

47 minutes ago, neilestrick said:

have you used your laser pyrometer to compare the temperature difference between bricks and the metal banding on electric kilns?

I have measured after refractory coating with the flir (gas kilns) but only anecdotally it is so hard to correlate one firing to another objectively.. Always wanted to paint the inside of a lid and bottom of a regular electric kiln which would have provided a good platform to get real data. Had the ITC 100 left over too. Just too chicken at the time or worried it would eventually flake off the kiln lid.

Edited November 27, 2020 by Bill Kielb

[neilestrick]

I'm firing this weekend, if I have a chance I'll take some measurements.

[Bill Kielb]

5 minutes ago, neilestrick said:

I'm firing this weekend, if I have a chance I'll take some measurements.

It’s tough because if it’s a  laser you need to recalibrate for emissivity.

[neilestrick]

2 minutes ago, Bill Kielb said:

It’s tough because if it’s a  laser you need to recalibrate for emissivity.

Yeah, my laser has adjustments for that. I'll see what I can do.

[Christiane77]

not getting a crack in the lid is worth not doing that... might think a little longer before trying... thank you for your answers! 

[Mark C.]

3 hours ago, Bill Kielb said:

I have measured after refractory coating with the flir (gas kilns) but only anecdotally it is so hard to correlate one firing to another objectively.. Always wanted to paint the inside of a lid and bottom of a regular electric kiln which would have provided a good platform to get real data. Had the ITC 100 left over too. Just too chicken at the time or worried it would eventually flake off the kiln lid.

Bill

I sprayed a Skutt 1027 -inside walls and lid-it was a sitter no timer kiln I just bisqued in it . At that Time I had just bought a 1227 and never fired that 1027 but a few times after that. I sold it last spring to a person who is doing low temp. Bisque on pots  to be used for a wood fire  -perfect use for a kiln that manuel and that low temp. The lid and walls where pristine after all those decades .

I also sprayed my car kiln soft bricks -I'll look to see if I did the inside arch. The walls where sprayed and then put a layer of fiber inside the wall  over the brick and sprayed that. Back in the Day Fritz (ITC invented and long ago owner who sold out) used to give me a great deal on his products. That layer on the bricks is still holding well as some of the fiber in bag wall came off after 20 years and the bricks are still holding the materials well (thin coats are key)

My car kiln wall is 4.5 inch hard brick (I like that look) and 4.5 inches soft brick-mostly k26 and some k28s and in some areas 1 inch high temp fiber over the soft bricks.. Maybe 750 -1000 fires 

in 3.5 decades -average 25-30 cone 10 glaze fires -not counting the exact same number of bisque fires (I never count bisque fires in totals)

I also sparked at least 60 shelves with it top and bottoms and sides-Those where English dry pressed 1 inch thick 12x 24s. Never had any ITC come off.  I also sprayed at least 20 -20 advancers top and bottom maybe more. I used to use that stuff everywhere as it reflects radiant heat very well. Its main use in in industry to select heat in huge kins and such. I also have my own special coatings now that holds well. I use a zircon mixture in firebox area on any material(fiber -soft and hard brick)  and it never comes off. That mixture is milled zircon added to a small amount of  liquid colloidal silica. I have another mixture that resits salt as well but it proprietary to me at this time (not sure what my future plan are with that)

I have been thru more gallons than I care to recall. The new owners priced it out of site now. I still have some. I coated a salt kiln in Molokai a few years ago with some of my old stash of it.

Now I only wash the tops sides of advancers . The its after about 300 cone 11 fires tends to bead up  like salt pebble up on advancers-then I grind it smooth. Never comes off

I loved the rejectivity of this material-that was mostly in the 90s  and early 2000s for me. The love affair is over now after Fritz sold the company.

I still use the ink pens and hat he sent me long ago. ITC is good stuff

 

Edited November 28, 2020 by Mark C.

[Bill Kielb]

20 minutes ago, Mark C. said:

I still use the ink pens and hat he sent me long ago. ITC is good stuff

It’s crazy expensive now but it definitely works. How much? Never measured it really, I have used it strictly to extend the life of soft bricks / soda fire but liked it so much just started using it on reg gas firing soft brick for the energy benefit. Looks good on the IR camera but never really formally measured . Sorry to hear your guy is gone.

[Mark C.]

22 hours ago, Bill Kielb said:

It’s crazy expensive now but it definitely works. How much? Never measured it really, I have used it strictly to extend the life of soft bricks / soda fire but liked it so much just started using it on reg gas firing soft brick for the energy benefit. Looks good on the IR camera but never really formally measured . Sorry to hear your guy is gone.

His wife died If I recall and his heart was not in the business anymore. That was years ago.

Edited November 29, 2020 by Mark C.

[Sorcery]

Anything preventing air from reaching the bricks is going to help them retain more heat.

If there wasn't a better workaround though, someone would be selling "kilnfoil".

I read once of someone doubling up lids.

Sorce

[MKG001]

I noticed my Skutt kiln seems to radiate a LOT more from the top than from the stainless steel sides, and I think it is because the emissivity of the stainless steel is much less than that of the firebrick.  Was thinking of just layering aluminum foil over the top... but don't want lid to crack per @liambesaw.

thx

Mike