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docweathers

Deep purple precipitating out hard flat chips

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Yesterday I mixed up 500 g of deep purple. Today I went back to use it and it had precipitated out about 1/10 of its volume in hard flat chips. I tried to grind these chips with a mortar and pestle and was not successful getting him to go through an 80 mesh screen. This is not pancaking  sludge on the bottom. It is very brittle hard little plates, Anybody have any idea what would cause this?

Here is the recipe I used
Deep purple

Custer feldspar          27
nepheline syenate      14 
silica                                     33
Whiting                             12
magnesium carbonate   1.7 
Gerstley borate           8.6
lithium carbonate       3.7
tin oxide                           4.8
chrome oxide             .17 
cobalt carbonate         .6
bentonite                     2.

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Ill get hard soluble salt deposits on the edges of my buckets, where the water line meets the bucket, that have set around for a while, and evaporated some. Doesnt happen with all my glazes, just a couple. However, it has never happened to me overnight, and Ive never gotten big chips/chunks like you say.

  After you mixed the glaze yesterday, did you sieve it then; Then you came back today and found it had formed these chips?

Curious to know what the glaze masters have to say here!

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Well there's like almost no clay in there, so hardpanning is probably gonna happen.  Was it cold? Possibly frozen?  Cold makes crystals precipitate.  Looks like you have plenty of solubles in there, lithium, gerstley, magnesium.  That's what I see when I see the recipe.  Instead of grinding them, try dissolving in HOT water.

Edited by liambesaw

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Agree with Liam.  At a glance, I'd say calcium boron crystals if they're flat, but neph Sye and lithium can be culprits as well. Take some of the water off the top of your glaze and heat it with the crystals in it, and add the dissolved stuff back in the bucket. That way your glaze won't get diluted if you don't want it to.  And if to can keep your glaze in a warmer spot it will slow the crystallization down. 

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So you think my 35° studio is the problem. :o How warm do I have to keep this stuff so it won't crystallize?  I haven't had that problem with other places.... Why deep red?

No,  I did not filter it after I mix it up but it looked pretty good.  

 

Thanks for your help

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15 minutes ago, Callie Beller Diesel said:

35! I’m Canadian and I don’t work in those conditions!

Your studio probably has insulation!  Mine is just a plywood and 2x4 shed, no insulation.  Usually we don't need any insulation but it's been unseasonably cold here in Seattle so I have to fire up my buddy heater when I'm working out there.  Nothing heats up a little shed like 15,000 British thermal units!  

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Haha! @liambesaw my studio is indeed in an insulated basement currently, but I have worked in many an uninsulated garage in a place that cools off drastically at night because of the altitude. It's time to call it when the temps don't get above 10 C.

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35° is what it is when I go out there in the morning to turn on my heaters. But the glaze has been at that temperature for 10 to 15 hours. I try not to go out there until the temperature comes up to at least 45° My pottery studio is in one stall of my garage, which is well insulated. My welding studio is in another stall. I don't do much welding in the winter because I have to keep an overhead door open because of the nasty gases off of the torch.

What's this Buddy heater? 1500 BTU, I think I should get one. 

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23 minutes ago, docweathers said:

35° is what it is when I go out there in the morning to turn on my heaters. But the glaze has been at that temperature for 10 to 15 hours. I try not to go out there until the temperature comes up to at least 45° My pottery studio is in one stall of my garage, which is well insulated. My welding studio is in another stall. I don't do much welding in the winter because I have to keep an overhead door open because of the nasty gases off of the torch.

What's this Buddy heater? 1500 BTU, I think I should get one. 

Makes for a quick warm studio, I swear it gives me a sunburn though

IMG_20190205_223833_crop_449x604.jpg

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25 minutes ago, docweathers said:

Is it safe to use indoors? I.e. what about carbon dioxide and carbon monoxide?

You only live once!  It does generate the various carbon gasses, but my shed isn't exactly air tight.  I fully expect to die one day, but not from my buddy heater

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Indoor safe heater

Outdoor-only heaters, such as propane tank mounted radiant heaters and portable forced-air propane and kerosene heaters (sometimes called “torpedo heaters”) have traditionally been used at work sites and football sidelines. When these types of heaters are brought inside a, residential home or garage, the risk of CO poisoning is significantly increased.

CO is a colorless, odorless and highly poisonous gas that is produced from incomplete combustion. CO interferes with the blood’s ability to transport oxygen to the lungs and can result in flu-like symptoms including headache, nausea and dizziness. Increased exposure without exposure to fresh air can lead to death by asphyxiation.

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Yeah, mine says it's rated for indoor use in ventilated areas but not in living quarters so I live on the edge!  I definitely wouldn't bring it inside of my home, it sometimes hiccups and throws a little fireball at me when I start it, more worried about burning the shed down

Edited by liambesaw

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@liambesaw Get yourself an electric infrared heater; more energy friendly. Infrared doesnt heat air space, only objects which contain water (humans...); just point it at yourself and enjoy! Very minimal risk of fire, better on operating costs, and no risk of CO poisoning. I agree, that with enough ventilation (likely have in your shed) its not a huge chance, but if you had a low pressure day, and no wind, you might get a buildup; a lot of manufacturers advise cracking a window when units like these are used in enclosed spaces.

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small safe heaters are not that expensive @liambesaw  Seriously!!   And to just comment on Doc's glaze question, I have that same problem with any of my glazes that have lithium in them.  It seems to me that I get those flat crystals when it is cold or when it is hot.  We run wildly drastic temps here.   I did not know neph sye could do that as well.

Roberta

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6 minutes ago, Roberta12 said:

small safe heaters are not that expensive @liambesaw  Seriously!!   And to just comment on Doc's glaze question, I have that same problem with any of my glazes that have lithium in them.  It seems to me that I get those flat crystals when it is cold or when it is hot.  We run wildly drastic temps here.   I did not know neph sye could do that as well.

Roberta

I have a small safe heater in there, i use it to keep everything from freezing, but it doesn't even begin to heat the shed to 80 degrees like the Mr heater!  I can run mr heater for 10 minutes and turn it off and bask in the warmth, I'm really not concerned!

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Before going too far along on assuming that heating will 'fix' the crystal formation, I suggest that Doc try making small batches without the specific component you expect as 'the culprit' forming the crystals.   test to see if the crystals form, if so then address the solubility of that component to see if warming the slurry will help.  

Lithium carbonate is more soluble in cold water than in warmer water!!!! if lithium is "the culprit",  warming the storage will make it worst, not better.   

LT

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