LOWELL BAKER on thu 10 dec 98
This is the stuff that burns up in the firing. Ignoition loss or
loss on ignition.
Paul Raymond on sun 30 may 04
I have been reading the post following my initial question about LOI and
so far this is what I have come away with. There is a large range of
temps as to when organics burn out, the greatest amount of which is
water. Second an additional soak may be of use somewhere between 977
degrees and 1500, although soak is probably the wrong word. Perhaps a
slow down in temp gain is a better way to describe this period of a
firing.
When I used to help my friend fire to cone 10 we always took it quite
slow around 900 to 1000 degrees because of the quartz inversion, as
Carol Tripp said in her post. He told me that moving through this range
too fast could crack the pots.
So it seems that there is a large degree of debate on this subject. I
think I need to digest this because there is still a lot that I do not
understand. I just need to think outloud in order to work towards
understanding. Looking forward to reading more!
Paul
Paul Raymond
Franklin, Tennessee
crazyrays@bellsouth.net
Ron Roy on wed 2 jun 04
Hello again Paul,,
Sounds like you would do well to get the Hamer book - your understanding is
going to get a lot better fast with it.
Slowing down through the quartz inversion on the way up is not necessary by
the way. Quartz inversion dunting happens on the way down.
On the way down - because rims cool faster than the feet - and go through
the quartz inversion (get smaller) then you can understand why it happens.
On the way up - the rims heat faster than the feet (get bigger) so it would
take a lot more pressure to crack a pot. In the first instance we ahve
tension - clay is not strong in tension - in the second instance we have
compression - clay can take a lot more compression.
See Hamers 10 pages on SiO2 in all it's forms for starters.
Never mind - there is no lack of misunderstanding about our craft among
potters - we mostly have choosen not to understand except what is absolutly
necessary to get pots out of the kiln.
Our solutions to problems are often based on hearsay and not on an
understanding of the basics - we do what we are told and have no way to
separate the good advice from the mistaken.
RR
>I have been reading the post following my initial question about LOI and
>so far this is what I have come away with. There is a large range of
>temps as to when organics burn out, the greatest amount of which is
>water. Second an additional soak may be of use somewhere between 977
>degrees and 1500, although soak is probably the wrong word. Perhaps a
>slow down in temp gain is a better way to describe this period of a
>firing.
>
>When I used to help my friend fire to cone 10 we always took it quite
>slow around 900 to 1000 degrees because of the quartz inversion, as
>Carol Tripp said in her post. He told me that moving through this range
>too fast could crack the pots.
>
>So it seems that there is a large degree of debate on this subject. I
>think I need to digest this because there is still a lot that I do not
>understand. I just need to think outloud in order to work towards
>understanding. Looking forward to reading more!
>
>Paul
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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