|
Posted by Bubbles_ on October 11, 2007, 7:31 am
Please log in for more thread options
> Let me see if I can rephrase into common ground. There are low fired,
> mid-fired and high-fired pottery. Low fire is typically your earthenware,
> raku, majolica, etc. Mid-fire can be functional stoneware, high fire is
> stoneware and porcelain of the translucent variety. Mid fire is what many
> people with small electric kilns are now working it. Your clay is
> vitrified (if it is a true midfire clay) at midfire range. It is not at
> lowfire . Typically the midfire range is cone5 to cone7 or 1183C to 1237C
> if you are firing @ ~60C/hr. If I were to soak at peak temperature I would
> fire to a lower temperature because the heat work would take me to the
> cone I want. The cone is a clay made to 'melt' with a certain heat work.
> What I want to know is when the clay and glaze is mature and this happens
> with heat work rather than just a certain temperature. That is why cones
> are important.
Hi D!
I fire to 1250 and prefer this because of the life in those glazes and that
the pottery is properly vitrified, so it can be used in the garden and I
don't have to take it inside in the winter.
The mid-fire glazes I have seen up until now have been a bit dull for my
tastes. I typically only use max 2 glazes (1 inside the bowl, one outside -
possibly 1 on the rim) on my pieces, so I really like for the glaze itself
to add life to the pot.
> Segments in my firing are simply different periods in the firing - so if
> you are running your kiln manually (without a computer program) you might
> run the first 6 hours with one switch on low and two switches off
> (assuming you have three separate controls). That would be one segment.
> The next 1 hour with 2 switches on low. That would be the second segment.
> The next hour with 3 switches on low. The fourth segment might be 1
> switch on medium and 2 on low. etc. So you are slowly coming up to a
> temperature you want. How fast you go from one temperature to the next is
> the ramp. Typically you go very slowly until all of the water in the clay
> has safely escaped from the clay. From there you can go fast until you
> get to the point with the clay changes physical structure. Here you want
> to again go at a rate where you do not get sudden fast changes. If you
> have glazes that form crystals you want to decrease the temperature slowly
> at the temperature where the crystals are forming. So you would not just
> turn off the kiln when it reached temperature and leave it. You would
> monitor it and when it reached the temperature you wanted to slow the
> cooling you would have it on low for a certain period (how you would do
> this manually would depend on how quickly your kiln cooled on its own).
I have a thermostat in my kiln. The controller is quite simple, and only
lets me put in 4 requirements.
time until
temperature (650 C always)
temperature to be reached
soak time
This has worked fine for glazes I use without this special "foredler"
(beautifier) on top. But the beautifier changes the glaze immensly and makes
it so lively with flares and beautiful highlighting colors (such as bright
blue in the black of the glaze).
> I know they use cones in Europe. Go to this site. The person is very
> nice and I am sure would answer questions (I would think she could tell
> you where and how to get cones). But there you can see what cone 6 glazes
> look like. She does a lot of testing. If you can fire at a lower
> temperature until you have more experience, I think you would find life
> easier.
>
> http://www.alisapots.dk/
WOW! I have driven through Aabenraa and even stayed there once! Every summer
when we drive up to Norway, we pass through Aabenraa! I will definitely get
in touch with her. Her homepage is really great as well - and how generous
of her to share all about her glazes!
> P.S. How do you know what temperature you are going to if you don't use
> cones? Are you doing this simply on timing given you are not sure if you
> are at 1270 or 1250? Communicating hard...
The thermostat in the kiln. Although this isn't 100% accurate. But if I have
been firing to 1250 and I increase to 1270, I know that even if 1250 is
really 1230 in the kiln, then I am increasing the temperature by about 20
degrees. Thus the new temp might in fact be 1250, but the important thing (I
thought) was to know what change I am making, and not necessarily the exact
temperature.
Also - the clay sinters at 1220 C - but can be fired at everything from 1000
to 1300 degrees. That means that I am well within the parameters as far as
that goes.
The glazes are for 1250 C.
Thanks for your time, D. I think that D stands for DEAR! :-)
Marianne
>>
>>>I just re-read this and am real confused - is that 1270 C? In which case
>>>you are firing to ~ cone 10?
>>
>> I do think that my kiln-computer actually shows a bit higher temperature
>> than the actual, so 1270 might be 1250. I would love to figure out a way
>> to test the hypothosis. Must ask my teacher on Friday if she has any
>> suggestions. As I said earlier, I have never heard of folk here using
>> cones.
>>
>>> Wow that must be hard to get to in a a small hobby kiln. How many hours
>>> does it take? Why are you firing that high? They actually have some
>>> pseudo porcelain at cone 6 (what I fire to).
>>
>> Well - I stopped watching over the kiln when it is firing, but I would
>> say something close to 10-12 hours to get to top heat. But that is with
>> my firing schedule as well. Actually, I use 2 different ones for high
>> glaze and have been adjusting them a tad each time because of the
>> problems with the bubbles.
>>
>>> This is my typical firing scedule (the hold brings it up to cone 6)
>>
>> I don't understand what you mean by segment, sorry!
>>
>> You fire to almost 1200 - my glazes are meant for about 1220 to 1270
>> according to the lables.
>>
>> I only have 1 hold on my computer, and that is at top temp. I vary
>> between 20 and 30 minutes - having tried 40 once, to no avail.
>>
>>> Segment Rate F hr(C hr) Temp F (C) Hold (min) Time (Hr)
>>> 72(22.2)
>>> 1 100(37.8) 220(104.4) 0
>>> 1.48
>>> 2 350(176.7) 2000(1093.3 0
>>> 5.09
>>> 3 108(42.2) 2185(1196.1)
>>> 0.33 1.71
>>> 4 -500(-295.6) 1900(1037.8) 0.17
>>> 0.57
>>> 5 -125(-87.2) 1400(760) 0
>>> 4.00
>>>
>>> 13.34
>>
>> D - thank you so much for taking the time to help me try to figure out
>> this problem! You are an angel, as are all the folks on here who have
>> such patience with a pseudo-beginner like myself!
>>
>> Hugs!
>>
>> Marianne
>>
>
>
| 
XML site map