On 7/1/13 8:19 AM, John Kuthe wrote:
> 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...
>
Not counting the release of steam, I'll guess it takes 80 watts to keep
a shiny cooker at cooking temperature and 160 watts for an oxidized one.