[cdt-l] Black pot = increased heat transfer?

Mark Jernigan footslogger03 at yahoo.com
Wed Dec 27 15:51:49 CST 2006


Not a physicist but did the following experiment earlier this year.  I tested for the differences between painted (black) and unpainted AND whether Titanium is better than Aluminum in terms of boiling time.
   
  Take it for what it's worth  ...
   
  ====================================
   
  Titanium vs. Aluminum -- Bare Metal vs. Painted Black 
  
---------------------------------
    Well sports fans ...here are the results you have all been waiting for.

First off, I have no intention of trying to prove or defend my results. Read, enjoy, reject ...I'll still sleep well.

WYSIWYG !!

TEST >> 

A) To see if there is any difference in boiling times between an Aluminum and Titaium cookpot

B) To see if painting the cookpots black has any effect on the performance (eg boiling time) of the 2 cookpots.

Materials: Evernew Titanium 1.3 Liter Cookpot and a somewhat generic 1.3 Liter Aluminium Cookpot (Walmart)

Stoves Used: 2 Trangia Westwinds with Denatured Alcohol.

Process A >>

Placed 8 oz of cold (tap) water in each cookpot

Placed 1 oz of denatured alcohol in each of the stoves.

Set stop watch to zero.

Lit both stoves and allowed the central flame to extinguish leaving only the ring of blue flame emitting from the top of each stove.

Placed the cookpots on top of the potstands and started the stop watch


Results TEST A >>

At approximately 3 minutes/30 seconds there were visable gas bubbles at the bottom of both pots. NO ...I didn not try to quantify the difference in the number of bubbles.

At approximately 4 minutes there were gas bubbles rising to the surface of the water in both cookpots. There appeared to be MORE bubbles rising in the ALUMINUM cookpot (for whatever that is worth)

At approximately 4 minutes/30 seconds there was a ROLLING BOIL noted in both cookpots.

==============================================
==============================================

TEST B >>

I then allowed each of the cookpots and stoves to fully cool. I dried off any visable remaining water from the cookpots and placed them upside down on newspaper and painted them black using Krylon Barbque Grill High Heat spray paint (Walmart). I did not measure the paint used. I pained one cookpot at at time and simply applied the paint until the base metal was fully covered on both cookpots.

I repeated the process outlined above in PROCESS A

RESULTS >>

The results were virually identical as outlined above for PROCESS A

CONCLUSIONS

1) Under the circumstances/conditions outlined above there is no significant observable difference in the boiling time of 8 oz of water using either a Titanium or an Aluminum cookpot and an alcohol stove.

2) There is no significant observable difference in the boiling time of either a Titanium OR Aluminum cookpot if it is painted black.

POST SCRIPT

I did notice that in the case of both (Titanium and Aluminum) cookpots, painting the undersurface DID reduce the tendency of slippage on the standard Trangia Westwind pot stand.

Therefore, although there is virtually NOTHING to be gained in terms of performance between a Titanium and an Aluminum cookpot, regardless of whether it is in its natural state or painted black, I have decided to paint the bottom of my 0.9 Liter Evernew Titanium cookpot black prior to my next backpacking trip to reduce slippage.

About the only other comment I will make is that I have heard/read that (unconfirmed sources) Aluminum is suspected to be linked to some health disorders. Who knows ...next year we might learn that Titanium and it's alloys are equally or even moreso toxic.

Please take the above results/comments with a grain of salt. This was meant as an experiment for my own edification and I just decided to share the outcomes for what it was worth.


Mark Dixon <mkdixon1 at excite.com> wrote:
  
I've always wondered why a blackened pot would increase heat transfer when cooking. Nocona said it in the last post. Since a stove emits long-wave radiation, the color of the pot should have no effect. If you were somehow able to cook with direct sunlight, shortwave radiation, a black pot would matter. Is the black stuff acting as an insulating layer? Any physicists out there to explain?

Mark

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