On Sun, 30 Jun 2013 18:58:19 -0400, j Burns >
wrote:

>On 6/30/13 6:35 PM, John Kuthe wrote:
>> On Sun, 30 Jun 2013 16:17:14 -0400, j Burns >
>> wrote:
>> ...
>>> Presto says their aluminum models have better cooking properties than
>>> their stainless models at twice the price. The advantage to stainless
>>> is that you can keep it shiny indefinitely. I've read that cream of
>>> tartar will shine aluminum cookware. Is that the best method?
>>
>> Why? Aluminum oxide is a protective free coating.
>>
>> John Kuthe...
>>
>I see your point. The 1939 model looks fine to me.
>
>Polished aluminum has an emissivity of about 0.05. Aluminum oxide has
>an emissivity of about 0.25. So if I kept the exterior polished, it
>would hold heat a little better... but I probably wouldn't notice the
>difference.

Plus a shiny surface is so much prettier. But you are correct,
relative emissivities are probably not gonna make much of a noticable
difference. Plus if you kept Al polished to a mirror shine, you'd
eventually polish a hole in your pressure cooker! ;-)

John Kuthe...