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Chris Campbell

Really, Really Basic Question

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My question would be why can't you get it shipped to you. I live in Louisville Ky and my favorite suppliers are in Indianapolis and Lexington, however both of them will ship to me via the postal service or ups. Unless shipping soda ash is a hazmat issue you should be able to to the same.

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Marcia -

I am mixing the soda ash mixture to brush on my porcelain to get a bit of flux and hopefully gloss, not shine. I want to start running the tests soon as I have a lot of work piling up that needs to be fired.

Dannon thought the rutile and the bentonite would discolor the porcelain. So I will be testing a simple concentrated soda ash and hot water mix.

 

Yes, I could get it shipped but that seems like a lot of trouble for soda ash. Find the number, find the credit card, call the order desk .... :wacko:

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Soda ash is an anhydrous form of baking soda.

 

I have made soda ash from baking soda:

 

Place the baking soda in a frying pan and heat it on high. The baking soda will " boil" as the CO2 comes out of the soda. Continue to stir until it stops boiling (offgassing). Once it has stopped, the soda is in its anhydrous state. You can also calcine baking soda in the kiln by heating the baking soda at about 350 degrees.

ELAINE BRADLEY likes this

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Soda ash is sodium carbonate.  Baking soda is sodium bicarbonate.  Heat the latter above 50 degree celcius causes thermal breakdown of the bicarbonate. One CO2 molecule is released as gas, leaving sodium carbonate.  This a clip from Wikipedia.  You can also reference Chemistry.about.com and search sodium bicarbonate's thermal decomposition.   Most texts suggest heating the baking soda above 350 degrees F for 1 hour. 

 

Also, the soda ash will reabsorb CO2.  So it is best to store it in a sealed, air tight container.  Many of the problems using old soda ash in glazes comes from the fact that the soda ash has recaptured water and CO2. When this happens its molecular weight increases and thus changes the glaze chemistry balance.

 

Mark, I do know what I am talking on this one.  I have a major in Microbiology and Chemisty.

 

Thermal decomposition

Above 50 °C, sodium bicarbonate gradually decomposes into sodium carbonate, water and carbon dioxide. The conversion is fast at 200 °C:[9]

2 NaHCO3 → Na2CO3 + H2O + CO2

Most bicarbonates undergo this dehydration reaction. Further heating converts the carbonate into the oxide (at over 850°C):[9]

Na2CO3 → Na2O + CO2

These conversions are relevant to the use of NaHCO3 as a fire-suppression agent ("BC powder") in some dry powder fire extinguishers.

curt and High Bridge Pottery like this

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Man, I just love this forum. Who knew you could cook baking soda to get soda ash. How would anyone know this? I just buy mine at my local pottery supplier.[soda Ash, that is.]

TJR.

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You are so right John ... but ..... I still have nightmares where my chemistry final is the next day and I haven't a clue about anything! Somehow the info goes into my brain but does not connect. Can you recommend a good basic book that will not cause a brain freeze?

 

p.s. ... so glad you had such a great time in Japan. Love that jet lag eh? ....is your brain back in the right time zone yet? :huh:

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Chris,

 

East to West jetlag is the worst! It is getting better........ but no....... my brain is still in some timezone somewhere East of here maybe toward the eastern side of the Pacific. It will hit the North ameican landmass soon.... then the cross-country jaunt. It typically takes about 10 days for me to revert to somewhat "normal" (if I ever am that).

 

best,

 

...............john

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Chris,

 

As everybody is saying soda-ash is anhydrous sodium carbonate and baking soda is anhydrous sodium bicarbonate. And you can

convert the bicarbonate to the carbonate by heating.

 

However, unless the lower solubility of the bicarbonate is an issue, I cannot see why you would not just dissolve whatever you've got and

paint it on. [Would adding CMC keep more of the salt near the surface, and/or reduce the sensitivity to touch typical of dried but unfired

Egyptian paste?]

 

Personally I would mail-order the soda ash, and use baking soda until you get it. I'd be tempted to order some pear ash at the same time,

to see the difference caused by switching between sodium and potassium.

 

The ashes are anhydrous, and need to be kept in an air-tight container.

 

Regards, Peter

 

Wikipedia refs if you want the details:

http://en.wikipedia.org/wiki/Soda_ash

http://en.wikipedia.org/wiki/Baking_soda

 

PS The labelling of 'simple' compounds in supermarkets and hardware stores in the UK is getting more and more uninformative, at the

same time as old-fashioned compounds are being replaced by newer compounds (usually either functionally better or more environmentally

acceptable). Often without changing the name under which it is sold. [Remember when Calgon was sodium hexametaphosphate?]. So

unless you buy baking soda from the home-baking shelf it may be difficult to know what you're getting. A quick look today suggests that

many water-softeners are now [organic] polycarboxylates rather than sodium compounds. Even more alarmingly I saw  sodium peroxycarbonate

sold as "soda crystals" [this is an industrial-strength cleaner containing hydrogen peroxide, definitely avoid contact with the eyes].

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Who knew you could cook baking soda to get soda ash. How would anyone know this?

One of the reasons to take/study some glaze chemistry.

 

best,

 

.............john

 

John;

Are you dissing me? I took glaze chemistry with Val Cushing. This topic never came up.

TJR.

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Who knew you could cook baking soda to get soda ash. How would anyone know this?

One of the reasons to take/study some glaze chemistry.

 

best,

 

.............john

 

John;

Are you dissing me? I took glaze chemistry with Val Cushing. This topic never came up.

TJR.

 

Of course not!

 

best,

 

..............john

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So, if I understand this, all of the rock hard bags of soda ash sitting on our shelves, I could pop back in the oven (smashing first with large hammer  :wacko: ) and re-constitute it?  Probably wrong word but you know what I mean........

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I believe there are several books that list common, house-hold alternatives/substitutes for glaze chemicals.  I've also noticed many terra sig recipes that call for the use of Calgon . . . although I suspect those were developed before the recent changes to Calgon. 

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This paper on the chemistry of the reddish markings on some traditional Japanese pottery

may be of interest to a few readers of this thread, as it relates to the use of alkali metals to

colour a clay body.

http://tinyurl.com/qzxgwn5

 

Regards, Peter

 

BTW potassium chloride forms the basis of many lo-sodium salt substitutes.

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