Kiln lid "caulk"?

[PotSherder]

I don't have IR pics or measurements, but it's a great idea.  I've heard that "normal" digital cameras are sensitive to IR (allowing night shots with IR LEDs), but I suspect that's only near-visible IR, not thermal.  But it shouldn't be too hard to make a slew of measurements.  That would at least give me info about side, top, and bottom insulation losses.  Not sure how to deal with lid leakage other than to prevent it, and I'm still thinking about that.

The chamber is 1040 in^2 (13x13x13.5) to allow room for the elements, and also to work with standard 2.5x9 rectangular IFB dimensions.

"Real life" has been keeping me away from this project lately, but about to get back to it soon.  I'll report here what I find out.

[Bill Kielb]

On 9/18/2019 at 8:04 AM, PotSherder said:

I don't have IR pics or measurements, but it's a great idea.  I've heard that "normal" digital cameras are sensitive to IR (allowing night shots with IR LEDs), but I suspect that's only near-visible IR, not thermal.  But it shouldn't be too hard to make a slew of measurements.  That would at least give me info about side, top, and bottom insulation losses.  Not sure how to deal with lid leakage other than to prevent it, and I'm still thinking about that.

The chamber is 1040 in^2 (13x13x13.5) to allow room for the elements, and also to work with standard 2.5x9 rectangular IFB dimensions.

"Real life" has been keeping me away from this project lately, but about to get back to it soon.  I'll report here what I find out.

It can make your life easy, I would consider it if  doing what you are doing

[PotSherder]

Gorgeous image!  I don't think I want to spend $2K+ for this quality, but you've got me seriously considering a cheapie 32x32 model like the $129 'Basic' on Amazon:

Hti HT-175, Infrared (IR) Thermal Imager/Gun/Detector with IR Resolution 1024 Pixels & Temperature Range from -4~572°F, 6Hz Refresh Rate

<https://www.amazon.com/Infrared-Detector-Resolution-Temperature-4-572°F/dp/B07LH18MZ4/ref=sr_1_20?gclid=EAIaIQobChMIp7uqsJH25AIVEfDACh1HYwv9EAAYAyAAEgJ32fD_BwE&hvadid=241924497558&hvdev=c&hvlocphy=9016853&hvnetw=g&hvpos=1t3&hvqmt=e&hvrand=9949078927261224880&hvtargid=kwd-20455471147&hydadcr=24664_10400965&keywords=flir+camera&qid=1569764163&s=gateway&sr=8-20>

I think 32x32 would be enough to do this job.  It's really a 'one-off', so I don't need pretty images as long as I can see general trends.

Thanks for the idea!

 

[PotSherder]

Sorry for the delay getting back to this.  Decided against the 32x32 IR viewer since it has a fixed (distant) focus, so I couldn't build up a detailed image by taking multiple low-res close-ups.  Seems fixed focus is standard on all the cheapie units.

So I proceeded with the original "kiln caulk" approach, using ordinary kiln wash mixed up to heavy slip consistency to be extruded through an old mustard squirt-bottle.  Originally, I had discounted this approach because I was fairly certain that by the time I had run a thick bead around the rim, enough water would have been absorbed from the start of the bead that it would have been too stiff for the lid to squish it properly when closed.  The trick I came up with was to line the rim with strips of ordinary waxed paper, which kept the bead out of contact with the rim. Closing the lid thus squished it evenly, as desired.  The waxed paper, of course, burned out completely in firing.  I tested this idea first on scrap chunks of IFB in a bisque firing, where I wasn't trying to reach peak temperature and wasn't worried about the lid leakage.  Afterward, the IFB chunks appeared to have a perfect seal between them, yet the top chunk could be lifted off with no effort.  The squished kiln wash had bonded only to the top chunk, not to the bottom one at all.

The subsequent glaze firing did make it to 1200 C as I wanted, but I have to say that I don't think the newly-sealed kiln lid had anything to do with that.  I just started early in the morning (5 AM) and used a faster firing schedule once above 100 C, reaching 1200 at 9 PM.   There was a little leakage glow visible around the lid, apparently due to the lid warping slightly so the side edges were a bit higher in their centers than the corners.  Didn't happen on the front and back edges.  (The upper element rods are just below the side edges.)

So it looks like if I want to fire in less time, I will indeed need more insulation.  The question is how much, and will it be reasonable regarding the cost and the added construction changes needed.  I'm thinking that there should be a way to determine the current k value from the cool-down time constant, but I haven't figured out how to separate out the portion due to insulation versus thermal mass.  If I could get a reliable measured k, I could compute the peak temperature to expect from added insulation.

 

[Bill Kielb]

On 10/19/2019 at 8:49 AM, PotSherder said:

Sorry for the delay getting back to this.  Decided against the 32x32 IR viewer since it has a fixed (distant) focus, so I couldn't build up a detailed image by taking multiple low-res close-ups.  Seems fixed focus is standard on all the cheapie units.

So I proceeded with the original "kiln caulk" approach, using ordinary kiln wash mixed up to heavy slip consistency to be extruded through an old mustard squirt-bottle.  Originally, I had discounted this approach because I was fairly certain that by the time I had run a thick bead around the rim, enough water would have been absorbed from the start of the bead that it would have been too stiff for the lid to squish it properly when closed.  The trick I came up with was to line the rim with strips of ordinary waxed paper, which kept the bead out of contact with the rim. Closing the lid thus squished it evenly, as desired.  The waxed paper, of course, burned out completely in firing.  I tested this idea first on scrap chunks of IFB in a bisque firing, where I wasn't trying to reach peak temperature and wasn't worried about the lid leakage.  Afterward, the IFB chunks appeared to have a perfect seal between them, yet the top chunk could be lifted off with no effort.  The squished kiln wash had bonded only to the top chunk, not to the bottom one at all.

The subsequent glaze firing did make it to 1200 C as I wanted, but I have to say that I don't think the newly-sealed kiln lid had anything to do with that.  I just started early in the morning (5 AM) and used a faster firing schedule once above 100 C, reaching 1200 at 9 PM.   There was a little leakage glow visible around the lid, apparently due to the lid warping slightly so the side edges were a bit higher in their centers than the corners.  Didn't happen on the front and back edges.  (The upper element rods are just below the side edges.)

So it looks like if I want to fire in less time, I will indeed need more insulation.  The question is how much, and will it be reasonable regarding the cost and the added construction changes needed.  I'm thinking that there should be a way to determine the current k value from the cool-down time constant, but I haven't figured out how to separate out the portion due to insulation versus thermal mass.  If I could get a reliable measured k, I could compute the peak temperature to expect from added insulation.

 

Seems like you could just add up the component transmission coefficient values and approximate. Maybe take some point measurements to confirm you are in the neighborhood of your calculated and decide on a percentage improvement needed. I used to teach this back in the day as a reasonable  way to approximate existing system U values mainly to address unacceptable dew points of  existing interior structures.

A quick way to approximate heat flow (Btu/hr), maybe Delta T/ 0.6  (Surface temp - ambient temp) /( film coefficient) where the coefficient for still air is approximately 0.6.  Answer would be Btu/ Unit of time. Then U(approximate) =[ heat flow] (as above) / [delta T] (Inside - minus Outside temp)  I would think on a comparative basis this would be representative enough to help you move in the right direction.

Just to add a thought, at some point if this is functional and since it’s oxidation, you  likely will need to have some “leak”  designed into the system.

Lots of cameras out there BTW for reasonable money these days

 

 

Just another observation: the L&L heat loss data show their 3” 2.5 cu ft kiln has total losses less than 2400 watts /hr.. (8067 btu) @ 2350 F.  Something is still odd with getting this to temp quickly. This thing should be able to make temp likely in 6 hours or less.