Crooked Lawyer Potter
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Posts posted by Crooked Lawyer Potter
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Gonna try the higher bique and see what happens. I'll let you know.
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I got the Leach glaze from Vaughn Smith. Its works beautifully for me (other than this issue)
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Callie
Yes the kiln is vented. I have always bisqued to cone 06 but changed just recently to 08, just to see if it made a difference in the glaze take-up. I think the current problem appears in both instances -- cone 06 and cone 08 but I am going to make sure by further experiment. Thanks for your input.
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No differences. Mugs (and other pots) are dipped using tongs. First glaze (ash) is allowed to dry before 2nd dip in David Leach II.
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I need help figuring out this glaze defect. I've gotten these mugs just where I want them except for this issue. The defects do not appear anywhere except in the interior of mugs or glasses. So, for instance, it is never a problem with plates or bowls. I'm thinking it must be related to the different conditions that arise in the tight confines of the mugs interior (higher heat, perhaps?). The mugs are dipped first in an ash glaze, allowed to dry, and then second dipped in David Leach II. The ash glaze is 50% ash, 50% red slip. David Leach II is :
potash feldspar 45
dolomite 15
frit 3124 5
EPK 15
Silica 10
Talc 10
colorant (iron ochre, or copper carb, or cobalt carb)
The clay is Laguna WC436. Its an oxidation firing in an electric kiln at cone 6 with a slow cool. The bisque was to cone 08.
Anyone have any ideas as to what is going on here? (The hole looks to me as if it goes all the way to the clay.)
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Will take this to heart. I love pottery but it does not match well with my congenital lack of patience.
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11 hours ago, Jeff Longtin said:
Also, have you allowed the pots to dry thoroughly before firing? This happens to me a lot, with my slip cast mugs, if I fire before the glaze has dried.
Curious about this idea. I DO often start up the kilnfiring without letting the glaze get good and dry, but I always start the fire program with a 2 to 5 hour pre-heat that I assumed would take care of the issue. What do you think?
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I may have asked this before, but this business of "viscosity v specific gravity v deflocculation" keeps me in a state of confusion.
For instance, if I want to "thin" the glaze I could: (1) add water - thereby thinning it and lowering its SG, or (2) deflocculate itthereby thinning it but keeping its SG the same, right? Is there a reason to do one over the other?
And, is "thinning" it the same as making it more "viscous"?
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So ... lower the viscosity? or lower the SG? Or a quicker dip?
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What do you call this glaze defect? Bisqued at 06, electric fired at 6. Long dip of Fat Cream with an ash glaze rim. BMix. It seems to happen randomly.
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Listmates
I've have some pit-fired cruets that I want to use as olive oil containers. I know that the relatively low firing temp means they are not fully waterproof so I have treated the inside with a stone sealer that is labeled "non-toxic" and "safe for food preparation areas". Any thoughts on whether this is safe for the intended use?
And how does one go about getting such a determination? Are there labs that will test it?
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A picture is worth a .........
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12 hours ago, Babs said:
Why not get any container, tare to zero with container on board.
Add 100ml of whatever then move decimal point accordingly to get the SG...just saying
I'm a sucker for a system. I did not like having to carefully fill those skinny beakers to the 100 g line and then weigh, rinse out, etc. I had this 80 g syringe in my studio so I weighed it empty and noted the result (28g). Then I prepared a chart in Excel that worked out all the SG numbers between 1.0 and 1.75 and stuck on the studio wall so that all I had to do to test SG was to draw glaze into the syringe to the 50 g mark and then lay it on the scale. I then looked at the chart to see the corresponding SG. Sounds complicated I know but its really simple once done and very handy. It looks like this:
Scale says: Less 28g (syringe) X2 =SG
99 71 142
100 72 144
101 73 146
etc all the way from 100 to 175
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32 minutes ago, Babs said:
You state you have tared the scale ,Dick's 1st question and then go on to take the weight of syringe off again in second part of your reply. If tare scale , don't then take weight of syringe off before x 2..
Again, my bad. Careless response. I just meant that when i weigh the syringe, the scale is tared to zero. In other words, the reading i get is the weight of the syringe and its contents. And since i know (or thought i knew) the weight of the syringe, i subtract the syringe weight to determine the weight of the 50g of terra sig in the syringe.
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4 hours ago, Dick White said:
Have you tared the scale to zero with the empty syringe on it? If so, then subtracting the 28g for the weight of the syringe has already been done by the scale. Even then, it isn't making sense. 2 X 70g would give a S.G. 1.4, which is almost glaze slurry consistency, or waaay too thick for terra sig.
And just for theory, the specific gravity of water plus a solid in suspension cannot be less than 1.0 unless the solid is actually floating on top and thus displacing more water in the syringe than it weighs. As noted above by Min, clay (regardless of the particle size) has a density/specific gravity in the 2.6 range.
Yes i tared the scale.
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Mystery solved! I weighed the syringe again and found the error. I had recorded its weight as 28g but its actually 23g and a re-weigh of the full syringe was 75g this time not 70 as before. So, 75 less 23 is 52 x 2 is 104.
Thanks to you all for your input. I'm going to assume that SG cant be less than 1 after all.
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3 hours ago, Dick White said:
Have you tared the scale to zero with the empty syringe on it?
Yes.
3 hours ago, Dick White said:Even then, it isn't making sense. 2 X 70g would give a S.G. 1.4, which is almost glaze slurry consistency, or waaay too thick for terra sig.
I'm not doubling 70. I take the reading of 70 and subtract the weight of the syringe. I then double that number. (42x2=84)
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2 hours ago, PeterH said:
Can you repeat the measurement process again? Once with t-sig and once with water?
Will do.
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1 minute ago, Min said:
70 mg (micrograms) would be 0.07 g (grams), I believe you meant 70g for the terra sig and 28g for the syringe?
Correct. My error.
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I draw 50 ml of the terra sig into my syringe and weigh it. It weighs 70 mg. I subtract the weight of the syringe (28mg) and then double the number, as in:
(70 - 28 = 42) x 2 = 84
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36 minutes ago, Min said:
doesn't make sense your sg is below one given ball clay has a sg of 2.5 - 2.6
Min
Good point. But consider -- this is just the smallest (and presumably lightest) elements of the ball clay.
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1 hour ago, Crooked Lawyer Potter said:
I used a syringe and scale.
I'm getting used to the idea that it CAN be less than 1.0 since as I just read SGis a measure of "relative density" and if the "solute" i.e the material floats in the solution it means it is less than 1.0 and if it sinks in the solution it is greater than 1.0
I guess the tiny platelets of clay are less dense than water and thats why they stay suspended (i.e. float) in the liquid.
But I will wait to hear from someone who actually knows what they are talking about.
2 minutes ago, Min said:BTW people are just trying to help here.
You would think that a lawyer could communicate better than i have here. I meant to express that my musings about “tiny platelets” was just the uninformed ramblings of a non expert and should not be taken as authoritative. Instead, i just came off sounding like an ungrateful ########. My apologies to those who were offended by my careless language.
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On 10/5/2022 at 1:07 PM, Callie Beller Diesel said:
A 40% solution would be 40g of dry material to 100g (or ml) of water.
I may be misreading your answer, but wouldnt that result in a solution that is 140 grams, of which only 40 grams are ferric chloride? Is that a 40% solution or a 35% solution? (140/40=35).
Perhaps this as simple as Chilly suggests above -- 40 grams of FC and 60 grams of water.
Mystery Glaze Defect! Help Please.
in Studio Operations and Making Work
Posted
What are the characteristics of a liner glaze? Does the term simply denote its position and function in the interior or are there certain qualities distinct from regular glazes?