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Soda Ash

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#21 smastca

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Posted 31 August 2013 - 05:58 PM

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........



#22 jrgpots

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Posted 31 August 2013 - 06:18 PM

After getting it ground back to a powder, you could bake it at 350 degrees for 1 hour or until offgassing stops.  It would be Sodium carbonate again... yes.

 

Jed



#23 bciskepottery

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Posted 31 August 2013 - 07:33 PM

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. 



#24 PeterH

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Posted 02 September 2013 - 07:48 AM

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.



#25 Chris Campbell

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Posted 03 September 2013 - 07:34 PM

Thank you all ... Testing will begin soon with hopefully excellent results.

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#26 PeterH

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Posted 06 September 2013 - 06:26 AM

Chris,

 

You might also try adding borax to your mix, hopefully the boron will reduce the temperature

needed to produce effects (if that is a problem for you).

 

 

I attach a couple of entries from an old clayart posting at http://www.potters.o...bject14497.htm/

 

Regards, Peter

 

Peter Atwood on tue 12 jan 99
Got yet another question for you. I recently tried for a soda effect on a small bisqued test pot

by brushing a mixture of soda ash and water onto the pot. I used white stoneware so that I could

really see the final effect and applied the mixture liberally. Then I fired to ^10R.

The result was this: Shiny dark orange flashing on some areas, pale shiny finish on others, and

crusty yellowish barnacle-like blisters on the rest. The inside seemed to have burned away

completely and left nothing but bare clay.

I'd like to achieve a controlled orange flashing effect. Is there something else I could try to get this to

happen? Even if the flashing is sporadic, is there a concoction that will at least be devoid of blisters?

Any suggestions would be much appreciated.

Sharon Pollock-De Luzio on fri 15 jan 99
Try dissolving the soda ash very well with hot water and spray it on the pots. I have used a regular water

bottle sprayer. With trial and error you can learn to control this quite well. WORD OF CAUTION: soda ash

is very caustic. Wear respirator, gloves, eye protection, long sleeves.
 



#27 terrim8

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Posted 31 December 2016 - 11:47 AM

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.

 

 

Gail Nicols uses "light soda ash" in her recipe for soda firing. This refers to calcining the soda ash.  So I'm not going from bicarbonate to carbonate. What temp & how long & what is the end product- the oxide? 



#28 terrim8

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Posted 31 December 2016 - 01:07 PM

Is NaO2, the oxide called "light soda ash"?



#29 Magnolia Mud Research

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Posted 31 December 2016 - 01:48 PM

soda ash is sodium carbonate.

 

The light vs dense soda ash is outlined here: (Solvay is one of several major suppliers of soda ash) -
http://www.solvay.co...oda-solvay.html

 

Light soda ash is a granular form that is best described  as "fluffy". 

It has a low bulk density and small particle size

 

Dense soda ash is less fluffy and larger particle size. 

 

The difference is that the light soda ash particles are porous and the dense soda ash particles are not porous.

 

Light soda ash dissolves more rapidly in water and worked best for Nichols' technique of making 'chunks' of a mixture of whiting and soda ash and water that solidified.  

 

If you are spraying soda ash either will work just as well.  

Soda ash is anhydrous when shipped by the manufacturers, but exposed to humid air it will slowly absorb water to form a soda ash hydrate.  The effect of this is that 100 grams of powder of a hydrated soda ash will have less 'active' ingredient than 100 grams of anhydrous material.  Hydration also causes the free-flowing powder to form somewhat hard lumps.

 

 

LT



#30 terrim8

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Posted 31 December 2016 - 02:57 PM

Thanks.

It would be easier if our ceramics supply store was open next week.

 

I just found this process from a paper discussing the Solvay process on an industrial scale and they start with the bicarbonate.

 

"2.1.2.6. Sodium bicarbonate calcination Sodium bicarbonate cake is heated (160 to 230°C) to achieve calcination into a solid phase «light soda ash» and a gaseous phase containing CO2, NH3 and H2O. This gas is cooled to condense water and the condensates formed are sent to distillation for NH3 recovery, either directly or via filter wash water. After cleaning, the gas (high CO2 concentration) is compressed and sent back to the carbonation columns (CO2 recovery cycle in Figure 2). Normally, energy needed for sodium bicarbonate calcination is provided by steam that condenses in a tubular heat exchanger which rotates through the sodium bicarbonate. The method consisting of heating externally by gas or fuel oil combustion in a rotating drum containing sodium bicarbonate is occasionally encountered. "

 

I want to try it but I'm afraid the house will smell like ammonia!( I wonder if it would clean the oven) (can't afford a new oven) (going to wait for the store to open or just use the spray method)



#31 Diesel Clay

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Posted 31 December 2016 - 03:04 PM

Terri and I are doing a soda firing next week, and the light version of soda ash isn't usually available without a special order. We had hoped to try Nichols' "chunk" method rather than spraying.
She mentions in her book that in workshop settings, she has calcined dense soda ash to about 600 F, and it works in a pinch to create the plaster she uses. She unfortunately does not give a time frame for this stuff to be in the kiln. The Wikipedia source states that sodium carbonate begins to decompose from the monohydrate, presumably turning anhydrous at around 212 F/100 C burning off whatever water it's absorbed from sitting on the shelf, and presumably becoming more porous than it was (oversimplified). My question would be is she suggesting the 600 F temperature to expedite the process because time is at a premium in a workshop setting? Can I calcine some dense soda ash in my oven at around 212F or do I have to mess around trying to figure out if my manual kiln with no pyrometer is at 600F because they don't make cone 023 or lower? (022 is roughly 1100 F, depending on firing rate.)

#32 Magnolia Mud Research

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Posted 31 December 2016 - 04:57 PM

Callie,

 

None of the readily available soda ash or baking soda have ammonia (NH3) in it. 

The solvay article is describing the 'solvay process' of making soda ash from salt water and sulfuric acid.  None of the soda ash one the market in the US or Canada comes from that route, it is too expensive to compete with the Trona mined in Wyoming.  So you don't have to worry about NH3.


I suggest that you take whatever grade of "soda ash" you have on hand, dry it in your oven at say 250 - 300 F for a couple of hours, or put it the kiln on low.  You do not want to melt it.  You also need to keep the oven/kiln ventilated to avoid  CO2 buildup.  Cool it back to room temperature and the place it in a blender and blend it to a fine powder.  Use the fine powder to make the Nichols' chunks.  I think the key to the chunks is to get the dry ingredients well mixed and not have too much water.  The chunks should keep without problems. 

  

Sidebar -- Measuring low temps <400F in an electric kiln without Thermocouple.  
  
   I monitor my manual test kiln with a grill thermometer that goes only to 450 F.  It sticks in a peep hole and gives me data on the early heating period when I fire the kiln.  For the soda ash drying, you can also place an oven shelf thermometer in the on the kiln shelf with the containers of soda ash you put in the kiln to calcine it.  Just keep a close look on what is happening.
 

Or you could skip the drying step and just try making the chunks with the materials you have.

 

If it works, then use the chunks in the firing; if not, just spray a soda ash solution.  Use draw rings, or an equivalent, to tell how well the ware has been glazed, etc., etc...

 

I have not tried the Nichols  chunks, but have studied the soda firing process extensively.  My contention is that the chunks slow the rate of soda vaporization from nearly instantly using the spray technique to a small amount of vapor spread  evenly (nearly) over the time from throwing the chunk into the kiln until the kiln is shut down.  The large body of evidence is that both can produce good work.

I remember an old Alka-Selzer ad that said "Try it, you'll like it." 

 

Good luck and have a safe and happy New Year.

 

LT



#33 Marcia Selsor

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Posted 31 December 2016 - 06:35 PM

Speaking of the soda ash from Wyoming, I taught a soda kiln building workshop at Western Wyoming college back in the 80s and we used the local soda ash straight from the mine. Some over exuberant students poured a lot of soda ash through the top port in the catenary arch. When we opened the kiln, that ash had eaten a hole through the silicon carbide shelf. The pots came out very nicely!
Marcia
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#34 glazenerd

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Posted 31 December 2016 - 07:18 PM

250F is more than enough to drive off surface moisture (clumping). Soda ash is hygroscopic ( fancy word for "draws moisture from the air).  Calcining is done to drive off molecular H20: not needed in this case.

 

Absolutely do not mess with the Solvay process; of producing soda ash from sodium chloride and calcium carbonate Thinking this is where someone mistakenly got the 600F from??.  You do not need to be releasing chlorine gas in your work area. Sodium "chloride" is also the basis of hydro --"chloric" acid. Which is the reason Marcia shelf got eaten alive.(I suspect)

 

Sodium carbonate has been the basis of "soda glass" (window glass) for over a century. Safe, no toxic fumes.

 

Why not make a slip from soda ash and 2-3% bentonite: make droplets on a cookie sheet through your hydrometer: and bake them to dry. Should work.

 

Nerd

 

Edit:  sodium bicarbonate  Na2CO3  (CO3) off gasses.

Sodium chloride: NaCi- In the first oxidation state, is conversion to chlorine gas. The reason you do not want to be using the Solvay process or chloride/alkali (calcium) in your oven or kiln.



#35 terrim8

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Posted 31 December 2016 - 07:53 PM

So....

I have 2kg of  granular soda ash. I can put it in a big bisque bowl, turn the oven on to 250 and check hour by hour for fluffiness? (that's my kind of baking) Then weigh it quickly & put it in an airtight container and save it to mix with the baking soda and limestone, right? 

 

GaIl NIcHolS Soda MIx

Light Soda Ash . . . . . . . . . . . . . . . . . . 20 Sodium Bicarbonate (baking soda) . . . 30 Calcium Carbonate . . . . . . . . . . . . . . 50

100 %

Add 9 U.S. fl. oz. of water per 1 lb. (600 ml of water per 1 kg) of dry mix. Wearing gloves, mix the dry ingredients thoroughly, then add the water all at once. Stir until the mixture begins to set, then break it into small pieces.

Light soda ash is required for the setting process. A wet mixture of sodium bicarbonate and calcium carbonate will not set; neither will a mixture using dense soda ash. Sodium bicarbonate is not an essential part of the soda source, but it makes the wet mixture less caustic. Sodium bicarbonate is also inexpensive and readily available in the supermarket or from a bakers’ supplier.

As this mixture breaks down in the heat of the flame, water vapor is released along with the vaporizing soda. Water vapor helps to carry the soda through the kiln chamber, enabling good glaze distribution and evidence of flame movement on the work. Water vapor also appears to assist with soda dissociation and glaze formation. "



#36 Magnolia Mud Research

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Posted 31 December 2016 - 08:04 PM

sounds like a plan.  check it in about an hour and stir to bring the bottom layer next to the bowl up to the top

 

LT



#37 glazenerd

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Posted 31 December 2016 - 08:05 PM

soda ash is Na2CO3     Baking soda is Na2HCO3    only difference is a (h) hydrogen binder; which burns off

Limestone is calcium carbonate (whiting).   some mineral differences as in SI/AL ratio

 

 

Sodium bicarbonate is an amphoteric compound. Aqueous solutions are very mildly alkaline due to the formation of carbonic acid and hydroxide ion:

carbonic acid is very mild, but an acid none the less- so gloves is a good idea. Better reason, it will suck the moisture out of your skin,



#38 Mark C.

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Posted 31 December 2016 - 08:05 PM

I like spraying salt in liquid form. Our tries at spraying soda always plugged the sprayers so we made soda tacos-that is melted soda ash in hot water until thick cream and cream like and poured it into newsprint and folded into a taco shape and tossed these remade tacos into the worst inside bag walls while spraying slat into spray ports.


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#39 Magnolia Mud Research

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Posted 31 December 2016 - 08:24 PM

The reason most potters have problems spraying soda ash (or salt) solutions into a kiln is that they are greedy about water, they don't use enough.  to make things easy, increase the water so that all the soda ash or salt is dissolved, and there are no crystals left in the mixing bucket.  Spray this solution into the kiln using a pressure sprayer so that the mist is fine, not large drops. 

You will find that you can get a very good glaze layer, have more control over where the light and heavy coatings occur, and have less damage to the kiln.  Also the additional water will increase the reaction between the soda/salt and the surface of the pots. 

The  over simplified reaction sequences you read in the pottery textbooks for salt/soda firing are not wrong, they just are weak on being right.  The chemistry has been well researched and thoroughly understood since the late 1980's by researchers studying the combustion of coal and biomass and the corrosion in gas turbines.  None of this work has been published in the literature read by potters.

LT



#40 Mark C.

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Posted 31 December 2016 - 09:37 PM

The reason most potters have problems spraying soda ash (or salt) solutions into a kiln is that they are greedy about water, they don't use enough.  to make things easy, increase the water so that all the soda ash or salt is dissolved, and there are no crystals left in the mixing bucket.  Spray this solution into the kiln using a pressure sprayer so that the mist is fine, not large drops. 

You will find that you can get a very good glaze layer, have more control over where the light and heavy coatings occur, and have less damage to the kiln.  Also the additional water will increase the reaction between the soda/salt and the surface of the pots. 

The  over simplified reaction sequences you read in the pottery textbooks for salt/soda firing are not wrong, they just are weak on being right.  The chemistry has been well researched and thoroughly understood since the late 1980's by researchers studying the combustion of coal and biomass and the corrosion in gas turbines.  None of this work has been published in the literature read by potters.

LT

I'll try that next time . Our system has been to dissolve as much salt until there are no crystals then add a coup or two more of water and spray-this is all done with HOT water on huge pot on a burner.Maybe more water which cools down the kiln more and will take more recovery time can help us. Now we spray until temps drop way off and let it regain and repeat .We now have had zero issues with clogging with this technique. But as I said we make the soda into tacos as its 95% a salt fire only adding soda for extra foot colors


Mark Cortright
www.liscomhillpottery.com




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