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Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
Curing High-T paint on Your Pot on 04/19/2013 23:02:46 MDT Print View

I was wondering if anyone has bothered to "properly" cure the black stove paint on your Ti pot (if you bothered to go the stove painting route in the first place that is). If so, any special method you used? To the best I can determine the "curing" process involves raising the temperature of the painted object (after letting the paint dry for 24 hours) to 200 F for an hour or so, then upping the temp to 450 for another hour or more. In the process, apparently, some noxious stuff out-gasses, or I might be tempted to try my oven. I read somewhere that someone did it with a propane torch. Any thoughts?

This is suppose to make the paint more heat resistant and stronger - however for boiling water not sure if this is ever an issue. Perhaps it would be more scratch resistant.

Edited by millonas on 04/19/2013 23:07:08 MDT.

Jay Wilkerson
(Creachen) - MLife

Locale: East Bay
Curing High-T paint on your pot on 04/19/2013 23:18:24 MDT Print View

I have tried that on a few pots (Underneath) and it never worked out or it showed no difference in cook time! Then somebody on BPL told me that tactic is a myth and it is true! Waste of time.

Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
Re: Curing High-T paint on your pot on 04/20/2013 01:16:14 MDT Print View

I doubt it makes a big difference, but the paint adsorbs IR spectrum (heat EM energy) better than titanium - metal tends to reflect more radiant energy since it is a conductor. The IR, by the way, is the heat you feel when you face a fireplace hitting you in the face that goes away when you create a shadow with your hand or turn away. For example, when sitting around a campfire in the open the vast majority of the heat you feel is from the IR radiant energy. If you want to demonstrate to yourself the ability of metal to reflect IR you can reflect the heat from a fire onto your face using some aluminum foil - also one reason why it keeps your potato warm, but in the pot case why it does not adsorb as much heat from the thermal spectrum as perhaps it might given a little help. So yes, for cases where there is a good fraction of heat transfer due to radiant energy then putting almost anything on your bare metal would tend to increase that adsorption.

The color of the paint probably doesn't matter a damn in the infrared spectrum (what would matter is if it is black to an IR camera), but black (in the visual spectrum of humans)looks OK, and hides soot. This (radiant energy transfer) is only part of the physics that causes heat transfer to the pot, but it IS a part. The effect would depend strongly on the circumstances (proportion of radiant heat transfer vs. forms of molecular heat transfer), but there are several experiments, even here on BPL, by people who did careful measurements, that show a measurable effect. Nothing earth-shattering, but lets say %5 might be on the radar of the obsessive types here on BPL. It would depend entirely on how your stove was set up as the the fraction of heat transfer due to radiant energy.

I don't know if I can stand up to the authority of what "they" say (there seems to be a long-standing debate between "them-lore" and people who have tried to do controlled experiments on this), but I can say that the basic physics is sound as I have a PhD in Physics and taught it at the graduate level before I sold out. I'd suspect someone in the military might know what the best IR absorbing paint would be, but I also doubt we could afford it. Or even get it.

Anyway, I'm still interested in the original question - if anyone has heat-cured their high-T paint, for cosmetic reasons, or otherwise.

Edited by millonas on 04/20/2013 01:49:54 MDT.

Hikin' Jim
(hikin_jim)

Locale: Los Angeles, CA, USA
Re: Re: Curing High-T paint on your pot on 04/20/2013 06:30:47 MDT Print View

Mark,

I just sent a PM to someone here on BPL who I believe has done it. Let's see if he chimes in.

There are a lot of guys who have done stuff like that on Classic Camp Stoves which is a stove collector's forum. A lot of them are painting the cases, but I think high temp paint is high temp paint.

Lastly, I think you've got the right idea in terms of where the whole "blacking the pot" falls in the greater scheme of efficiency. There is some to be gained, but it may be hard to detect unless one is doing something specific to measure it. FWIW, I've got a section on Canister Stove Efficiency (Best Practices) (you have to page down a bit). I list blacking the pot as item number seven (out of seven). :)

HJ
Adventures in Stoving

Charles G.
(Rincon) - M

Locale: Desert Southwest
Curing by cooking. on 04/20/2013 06:31:54 MDT Print View

I know that this does not answer your question but using the pot for cooking is an uncontrolled sort of heat curing. I have two pots that I use, one aluminum, the other titanium. About five years ago I painted the bottom of each with Rustoleum High Temperature Grill paint. After the initial air drying period, both pots went into service. Yes, there was some minor out gassing of residual volatiles but nothing obnoxious. The paint coating is, after five years of regular use, still pretty much intact.

I ran a somewhat controlled experiment on heating times before and after the paint job with only the aluminum pot. I used a Pepsi can stove, measured volumes of water and alcohol at a consistent 65F with all trials at an air temperature of 65F and at 3400' elevation. Mean full rolling boil time with the unpainted pot was 4 min., 43 sec. with n=14. With the paint, after a couple of unmeasured boils to drive off volatiles, the mean boil time was 4 min. 36 sec. with n=14. The difference was significant at the 95% level. I know that others have not found painting to have an effect: I did but am not sure that the effect is worth the effort. I do think, however, that the black bottomed pots look cool.

USA Duane Hall
(hikerduane) - F

Locale: Extreme northern Sierra Nevada
Curing paint in an oven on 04/20/2013 07:10:50 MDT Print View

HJ sent an IM to me. I've only used high temp "VHT" paint on a couple flames for one of my vintage Optimus 111T stoves. Paint must be "cured to substantially enhance the durability of the finish and enhance chemical resistance". It involves placing the painted object after the paint is dry, in the oven for 30 minutes at 250F, cooling the item for 30 minutes, then repeating at 600F for 30 minutes, this chemically cures the paint, not to exceed the capability of the item being painted to withstand those temps. I'm single, so no opposition to using the oven. The painting process isn't very energy efficient, but not bad.
Duane

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Curing paint in an oven on 04/20/2013 08:07:37 MDT Print View

I painted the bottom of my Ti pot. After years, the center of the bottom has burned off (it's shiny) but there's still paint on the edges of the bottom and up the sides a little. I just let it dry for a few days. Black, spray, barbeque paint.

If it's black in IR, it will also radiate more, which will reduce some of the advantage.

Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
heat-curing on 04/20/2013 09:10:24 MDT Print View

Thanks for the replies on this!


"If it's black in IR, it will also radiate more, which will reduce some of the advantage."

Yes, that is true, but it will be radiating at the temperature at, at most, boiling water temperature, while it would be receiving energy (potentially at least) from thermal spectrum radiation at a much higher temperature (shifted higher in frequency and in energy), so this would be a small down tweak to what is already, admittedly, a small effect to start with.

I too was thinking that probably the obvious first thing to do would be to boil water for a while. That would possibly accomplish the first stage. As for the final curing temp the options seem to be trying to use my oven or wing it and blast it with a torch. Both have have their potential disadvantages. I will try one of them and post back here in the next day or so. At the very least if the oven experiment is a disaster I can let you folks know not to try it.

I'm not sure if the paint will ever be "scratch proof", but I *am* definitely wondering if it will at least make a difference the durability.

I should explain that the origin of my wondering about this came a decade ago the first time I tried painting a Ti mug with stove paint. I have to admit that, at the time, the "payoff" for me was as much from a Jardine-like desire to wipe the "snow peak" logo from my mug as from a curiosity to see if it did in fact make a difference in the heat transfer. LOL Anyway, I didn't do any heat curing at all, and the first time I put it on my canister stove the paint "stuck" to the pot supports and "melted" a bit, and pealed away. Perhaps some others may have had similar experiences. Since the paint was supposed to be good to 1200 F I wondered at this. Later I found out you were supposed to carefully drive away the resinous material in the paint etc. by heat-curing the paint before the job was done. Also, Ti may not be the ideal backing material for paint.

The paint is supposed to even look "wet" when you heat it the first time until the other materials in the paint are driven off. If you heat it too much before the process is finished it is supposed to blister, which might explain my experiences with using non-heat-treated paint for the first time.

Oh, FYI, I am only using hardware store variety stove paint - Rustoleum matt black high temp paint good to 1200, about $6-8 for a large size spray can. The stuff people use on their barbecues. I assume this is what the vast majority of people use.

Edited by millonas on 04/20/2013 09:37:29 MDT.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: heat-curing on 04/20/2013 09:49:11 MDT Print View

That's what I used - Rustoleum - still good on edges after years

Yeah, flame is 1000 F or whatever, pot is maybe 250 F, power is proportional to 4th power of temperature relative to absolute zero so pot won't be radiating that much

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Curing High-T paint on Your Pot on 04/20/2013 10:58:23 MDT Print View

You may want to check out high temperature motorcycle paint (use Google). Some of these paints are rated to 2000F. You also need to read the instructions. Some of these paints require special primer as a base coat. Last step is curing. If you have a wife, curing in "her" oven is a no-no. I learned about the oven "ownership" the hard way. You can buy a small roasting oven for under $50. This is what I did after the oven-Nazi caught me curing motorcycle parts in "her" oven; an oven I purchased before we met :(

You also need to determine if the paint is compatible with the metal you are using.

Now... My question is, why? My high temp painting experience is related to restoring my motorcycle. What does one gain by painting a pot; other than some (maybe) minimal incremental improvement in performance?

James Cahill
(DMATB)

Locale: SOCAL
rustoleum on 04/20/2013 11:04:30 MDT Print View

Rustoleums technical data sheet for the specialty high heat paint states "do not use on metal directly exposed to open flame". Although the paint is supposed to withstand 1200F (648C), the actual flames can get much hotter than that (depending on what you are burning of course) which may account for the peeling/flaking/sticking. Just a thought, and I have no idea if a slow ramp to temperature (curing) would change this.

Edited by DMATB on 04/20/2013 11:07:27 MDT.

steven franchuk
(Surf) - M
IR and efficiency on 04/20/2013 11:08:50 MDT Print View

This was posted on MYOG some time ago:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=73021

Basically the boil times for bear cans were measured. One had it's original pint. One was partially bainted black, another all black, and the final can had all pint removed.

The can with the original paint had the longest boil time. The all black can boiled water about 10 seconds longer. The can with no paint was the only one to boil water in less than 5 minutes, it was 30 seconds faster than the can with it's original paint and 20 seconds faster than the all black can.

Overall his result appear to indicate that IR radiation has a very small impact on boil times. Conduction of the pot is the biggest factor in boil times. An unpainted pot also weighs less than a painted one.

peter vacco
(fluff@inreach.com) - M

Locale: no. california
Re: Curing High-T paint on Your Pot on 04/20/2013 11:40:20 MDT Print View

i have no input on painting. but i know for an experienced fact that when i get sloppy and let the hard soot build up on my titi pot/bushbuddy combo, that it takes longer to boil.

i looked for the old (very) product Cal-Guard, which was a heat curable coating used on hot-rods and motorcycles, but could not find it anymore. it was hard as a whore's heart, and may have stood up to my soot scrape'ns.

cheers,
v.

Hikin' Jim
(hikin_jim)

Locale: Los Angeles, CA, USA
Re: Re: Curing High-T paint on Your Pot on 04/20/2013 11:43:03 MDT Print View

Now... My question is, why? My high temp painting experience is related to restoring my motorcycle. What does one gain by painting a pot; other than some (maybe) minimal incremental improvement in performance?
That's pretty much it, Nick. Personally, I wonder if it's really worth it.

In more practical terms, I think this applies more for someone buying a new pot. For example, getting an anodized aluminum pot instead of a plain aluminum one might offer some small incremental benefit in terms of heating efficiency.

You'll note in my link in my above post that I listed pot color last in terms of efficiency gains.

HJ
Adventures In Stoving

Hikin' Jim
(hikin_jim)

Locale: Los Angeles, CA, USA
Re: Re: Curing High-T paint on Your Pot on 04/20/2013 11:46:31 MDT Print View

i have no input on painting. but i know for an experienced fact that when i get sloppy and let the hard soot build up on my titi pot/bushbuddy combo, that it takes longer to boil.
Yes, it does. The built up coating acts as an insulator and reduces heat transfer. A clean pot is more efficient. Not an issue with gas, liquid (petroleum), and (most) alcohol fuels, but definitely an issue with wood and ESBIT.

HJ
Adventures In Stoving

Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
Re: IR and efficiency on 04/20/2013 12:09:38 MDT Print View

Providing the data collected above were collected carefully, then all you would have have "proven" is that for the particular setups IR is irrelevant to within a certain percentage. If you take a look at other people results posted here, some of which seem to have been done carefully, with enough repeats to quantify random variations in the individual tests and so forth, people have proven that there IS a measurable effect, in certain cases, between paint and no paint.

NO ONE has been suggesting it is a big effect. And it is "worth it". Pshaw! Such questions are unworthy in such an exalted discussion. LOL

Nonetheless, the thread you cite actually (by my analysis) does not show what you claim it shows, and appears to indicate that IR possibly *IS* playing a role. I don't believe the "paint as insulator" theory. OK actually I do, but lest talk hypothetically here. You would have to test this in carefully in IR free conditions to isolate it. By brushing the cans you in fact can reduce the reflectivity of the metal (for all frequencies of light with wavelengths longer that the irregularities of the final metal surface) which (if the results are to be believed) would *increase* the adsorption of IR - brushing would (probably) not have a large effect on the other forms of heat transfer unless you really gouged the hell out of the can. So it taken for what it is "proves" that IR *could* in fact be playing a measurable role, just that the best way of increasing the adsorption (by decreasing reflection) in this particular case was roughing of the surface, and not by paint. It is easy to imagine that you could rough up the surface to a greater depth that the thickness of the paint on an Al can which is very soft, and so it could potentially have a greater effect than paint. A cool idea actually! Not sure how well it would work for Ti, but is an interesting question.

As mentioned in previous posts above, what the paint looks like in visual spectrum meaningless for the question. Paint or no paint yes, beer can logo or black paint no. White paint of one type can easily beat black paint of another type for IR adsorption.

Also, I'd like to point out that there is zero data in that post on how an unfinished, unpainted shiny beer can would perform. I'm guessing that would be the worst of all. You could strip the paint chemically instead of roughing the surface and then test that. But it wasn't done.

Final summary: that experiment doesn't show what you claim it shows, but is pretty interesting anyway.

The paint weight is negligible.

OK, WAY to much time spent on this, however fun to think about. I need to get back to curing cancer.

Edited by millonas on 04/20/2013 12:22:49 MDT.

Hikin' Jim
(hikin_jim)

Locale: Los Angeles, CA, USA
Re: Re: IR and efficiency on 04/20/2013 12:22:04 MDT Print View

I need to get back to curing cancer.
Sell out. ;)

HJ
Adventures In Stoving

Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
Final Report on Heat Curing High-T Paint on 04/20/2013 20:44:59 MDT Print View

OK, I used my oven and no smells or otherwise noxious gasses beyond what you would smell with your oven cranked on overdrive. No brain cells killed, apparently, though I used my brain to determine that, so a bit of a catch 22.

Here is what I did specifically.

(1) Three coats of Rustoleum black matte stove paint (on Evernew Ti 0.9L, not that is matters). Let dry between coats. Face down on newspaper and Bobs your uncle.

(2) About 45 minutes in 250 degree oven. Took out pot and let cool, which happens almost immediately with so little mass of metal.

(3) Baked pot about an hour on the hi setting of broil.

Final result with the matte black (I have used a can of gloss for the past decade that finally gave out) is a nice dark grey. Much preferable according to my own aesthetics. Usually I sand down any paint on the lip, and I did this as well. Very nice results, no fumes to speak of. Possibly this is because of the very small surface area - come to think of it most of the sources that told me to beware of fumes were talking about full size stoves and barbecues.

Yes I know in the interest of scientific inquiry I should have done a scratch test comparison, but I just couldn't bear to do it given the lovely results. It "feels" really bonded to the surface. Maybe I will try it out on another pot at some point.

Final Analysis: (1) Aesthetic bliss - check. (2) No fumes - Check. (3) Apparent tough finish - check. (4) All corporate logos obliterated - check. (5) Improved efficiency - in doubt.

I will not bother with a final picture as that would be pure self-indulgence. Not like the rest of this exercise at all.

Edited by millonas on 04/20/2013 20:53:18 MDT.