Another soda ash wash thread

[rdrr]

I've been looking at the idea of using a soda ash wash to obtain some satin sheens and ideally introduce some flashing.  I can wood fire a couple of times a year but I generally only have access to a gas reduction kiln at the studio I go to and am hoping I can appIy this technique to get some different effects.   I know that experimenting and trying things out is the best way to see how this adapts to a particular environment and I intend to do that but hoping I can gather a little more information before I start.   With that said I a have a few questions that I hope some of you may be able to help with, especially wrt gar reduction environments.  

1.  Has anyone used this technique with flashing slips, how well did it work? 

2 If used with flashing slips do you apply the wash to the bisqued piece and then apply the flashing slip over that or is it the other way around?

3. Do some flashing slips work better than others? 

5.  Have you noticed that it works better in a particular part of the kiln, closer to the flame, in  the back, protected in the middle somewhere? 

6. Does it work any better on a particular kind of clay body.. stoneware, white stoneware, porcelain ...  ? 

7. Have you used it under a glaze and what are the results like? 

8. Does anybody have any examples of this technique that they would be willing to share?  I've seen this discussed in a number of places but there are very few if any examples that I have been able to come across. 

9. I know about over saturating the body and if it goes on too heavy it tuns a greenish color as well as making sure keep the bottom clean so it doesn't stick to the shelves but I am wondering if there is anything else I should avoid with this, any bad experiences?  

Thanks a bunch

Rob 

[Kelly in AK]

This sounds like a cool thing to explore, I can only guess what might happen. It may effloresce in different amounts on various parts of the work as it dries, which is an exciting thought. People into carbon trapping shinos use this property to great advantage. The other thing is that the soda will go into, not just on, your pot (I sense you already know this), so even if the foot is wiped clean I’d still either wad the work or make sure there’s a healthy coat of kiln wash on your shelves. Oh, and remember the stuff is caustic! That slippery feeling it leaves on your fingers is literally your skin being washed away. Use gloves and safety glasses. 

I’d love to know how the experiments come out. 

[ATauer]

My experience with soda ash washes is not directly related to how you use them, but I thought the information might be valuable because it involves using them with terra sigillatas which are a kind of slip, and though typically thinner and made out of smaller particles, I use Grolleg terra sig quite a bit which is at least a porcelain which most flashing slips are also. 

I use terra sig in a variety of ways, some fairly traditional but most of the time not traditional. I often fire it at cone 6 or 8 in oxidation, and lowfire it in raku usually at cone 06 but sometimes down to 1700F, which is often in-kiln reduced as well as the post fire reduction, so definitely different than high fire reduction but still legitimate reduction and not just post-firing. I use a variety of washes and often glazes over it, or leave it plain (or colored with mason stain and unglazed). In both oxidation and the lowfire gas reduction, the soda ash wash tends to leave, I’m not sure how best to describe it, whitish almost scum markings, which can actually look very attractive and are usually the reason I use it, because it makes that part of the ware look antique and old in a good way. To ensure I get that I apply a decent amount over the top of the terra sig in bone dry or bisque. If I want a sheen I definitely don’t use soda ash- which when applied under the terra sig has less of an affect on the surface but definitely doesn’t leave a sheen. I know it theoretically can with terra sig but I’ve never seen it actually happen with anyone I know, or myself, and I would think it would have a good chance of leaving white scum/scruff marks and dotting on slip as well.  

If I want a sheen I use borax or lithium carb washes instead. Often under the sig, that tends to lessen the amount of sheen possible by a little (not so much it makes a huge difference) but it dramatically reduces the odds that either will leave any marking or rough up the texture like putting the washes over the sig might. 

Not a lot to help you with, but the fact that soda ash washes leave, just pretty much every time, that whitish scum and spots and streaks on a different kind of slip just means I would urge some caution- and I know for a fact it does it in gas reduction as well. Hopefully it would do that less at cone 10 as it ideally should flux better, but I know people who have been disappointed with seeing those results after a cone 10 gas reduction. I would suggest while you are experimenting maybe trying out borax and lithium carb washes too, they can produce just gorgeous sheens on sig at cone 6 and would fully flux at cone 10, making them likely to have a stronger sheen/be quite shiny even in gas reduction as well, although I have no idea about flashing. 

Hope this helped a little, and wasn’t too different to be of use. 

Edited July 30, 2022 by ATauer

[Magnolia Mud Research]

8 hours ago, rdrr said:

I've been looking at the idea of using a soda ash wash to obtain some satin sheens and ideally introduce some flashing.  I can wood fire a couple of times a year but I generally only have access to a gas reduction kiln at the studio I go to and am hoping I can appIy this technique to get some different effects.   I know that experimenting and trying things out is the best way to see how this adapts to a particular environment and I intend to do that but hoping I can gather a little more information before I start. 

I have been using soda ash and/or baking soda solutions sprayed on areas of bisque and green ware for more than 10 years.  

The fired color surface depends on the clay body.
the appearance change of the fired surface is more a change in the value of the surface color of the fired clay body;   generally the color becomes more dark or stronger of the orange and yellow surfaces when treated with the soda application.  
a very white porcelain surface will show a faint graying in the white surface where the soda wash is applied.  
on a heavy iron clay body the surface will be darker where the solution was applied.  

I quit playing with "flashing slips" from any recipe and textbook about the same time I started spraying soda ash water;      instead, I spray the surfaces with the soda water and dust with various dry clays (kaolins  or ball clays) to greenware surface before the water soaks in; the soda water "glues" the clays to the surfaces and they may produce a crackled surface layer at the bisque and final firing steps.  sprayed areas with soda at bisque will show up with different values of the raw clays.  The amount of spray on an area is something that you develop yourself. 

I apply the soda -- get small spray bottles with a fine misting nozzle from the supermarket --- by spraying a little bit will make a change, a big amount will make a mess; somewhere in between is where you need to be; 
application by brushing requires careful not to get too much, you are not painting a house!   too much produces an area of "window glass glaze".  

The soda amount should be no more than 3/4 of the saturation amount; 
~1/2 saturation is about optimal.    I make my by adding soda to a bottle half full of water and when the soda quits dissolving I stop adding soda and fill the bottle with water.    Baking soda is easier to handle than soda ash; solubility charts for soda ash and baking soda are easily found in the manuals from the suppliers.  

location in the kiln is also an important variable along with any reduction variables;
fired in an electric kiln will also show effects, but they will be different than in gas or wood fired environment. once you find the "right spot" negotiate with the kiln operator to where you want your item located in the kiln.  

I have NEVER achieved a "greenish color" due to saturation of the surface with the soda;   once fired a cup that was soaked for three months in a soda ash solution; completely covered with soda ash crystals all over; it came out of the firing with a clear glassy coating -- similar to window glass, but no green; not very interesting either! 

applying "under a glaze" is the equivalent of adding soda to the glaze; that also goes to application over a glaze. exactly how much the soda changes the glaze recipe depends on the glaze application and the porosity of the bisque ware, and sometimes what you will have for dinner next week.  essentially the arrangement will be the same as two glazes overlapped. 
 
A final recommendation:  don't attempt to copy a color from an image in a book or from the computer as your target; spend your energy observing what you have available such as the clays and kiln firings, learn something about the materials you have already and the environments in the firing.  You will begin to make objects that no one else has nor can produce.  You will make the method your method.   

What started me down this rabbit hole was an attempt to make salt glazed wood fired ware in a college studio using the cone 10 reduction gas kiln without using salt or wood;   with some carefully application of baking soda, the right clay body, and some sea shells, the appearance was very close to salt/soda ware, fired with all the other studio ware, and the effort is no different than any normal glaze firing.  

footnote 1; for what it's worth: the right amount of soda added to kaolin can convert kaolin to Nepheline (not Nepheline Syenite) which starts to melt somewhere around cone 0; you can figure the ratios by looking up the composition of nepheline in a geology textbook.  this is one reason the method works.  

footnote 2: soda ash - the chemical name is sodium carbonate; baking soda - the chemical name is sodium bicarbonate.  limited chemistry data is available via wikipedia. 

footnote 3: adding other materials such as borax, and other materials moves the process away from soda to something else.  They may be useful, but the result is not what you asked about. 

LT

[rdrr]

 @Magnolia Mud Researchand @ATauer thanks for such detailed responses.  @ATauer, do you find the whitish/scum like markings appear anywhere you use the wash , even on bare clay body or just when it's covered with terasig or slip?   

[ATauer]

On 7/31/2022 at 9:56 AM, rdrr said:

 @Magnolia Mud Researchand @ATauer thanks for such detailed responses.  @ATauer, do you find the whitish/scum like markings appear anywhere you use the wash , even on bare clay body or just when it's covered with terasig or slip?   

Yeah, the markings appear on both the terra sig and the clay body, it seems to just affect any clay it seems, doesn’t matter if it is in slip form or from a body. It seems to stand out more over the terra sig though, it is not as noticeable on the bare clay, probably because of the color and sheen of the terra sig versus the matte clay- plus I have only used it on porcelains & porcelaneous stoneware so far personally so they are very white clays and the white from the soda ash isn’t very noticeable then. I am planning on using it on some speckled light brown stoneware and black stoneware I have soon though and I think it will stand out more on them. I feel like calling it scum makes it sound a lot worse looking than it is, I could also say it looks a lot like when your car gets scratched and has white marks, or a metal tin gets scratched, or even scratched antique wood- maybe that is a better analogy, because sometimes scratched antique wood looks very nice. If I’m using the soda ash wash instead of borax or lithium (both tend to have much more of a sheen, but can also leave some marks, the lithium especially I think if too much is put on kind of bubbles up, but they are much more consistent in leaving a sheen- I mean some people still use saturated borax washes or borax with minimal other ingredients to form a low fired glaze!) it is because I want the white marks which have a distinct look that makes the object look antique and old, my favorite is to use it over Grolleg terra sig colored with either the Bermuda or Celadon mason stains, which look a lot like an opaque burnished celadon/light turquoise, and put the soda ash wash over that and it looks absolutely gorgeous with those colors and the markings.

I usually try to avoid getting it on the bare clay but again with my clays it doesn’t show up much anyway. I’m thinking of trying it on my black stoneware on the raw clay, no slip or terra sig or glaze, I think it will look very interesting, since from what I’ve seen of it it works about the same on every clay, so I’m pretty sure it should develop the same on black stoneware. You can also adjust, with some degree of control although not totally, there are plenty of times I’ve put it on and it did want it is really supposed to do, leave a sheen with no white marking, based on how much soda ash you have saturated in your water how much of the scum stuff shows up, it can vary from very little to almost completely covering up all the terra sig. I try and usually aim for the middle ground, so I don’t use a completely saturated solution. Unfortunately I don’t have access to my notes right now about how much I use, it is something like a teaspoon or tablespoon of soda ash per cup of water, probably a teaspoon as a tablespoon for a cup of water sounds like a lot to me right now!

I’ll be very interested to hear your results. I’m hoping to begin doing some reduction firing soonish and eventually some soda firing, and I haven’t had any interest in flashing slips because I’m not a fan of the colors orange and brown/tan, which are most often the colors you get with flashing slips, although I do hear you can get reddish sometimes. But if washes alter how they look I might develop an interest in trying them. If only the flashing was a real nice red a lot more I’d be banging down the door to start using them. As it is, my plans to move to Europe in little over a year will result in me starting to definitely do soda firing, and maybe salt firing. I’m mostly interested in the wonderful clear glaze they can provide, and some of the affects of the process on glazes, colored slips, and underglazes you decorate with, without flashing or carbonization. I’m sure all the atmospheric people are shaking their heads at me, thinking about all I’m missing out on! I use soda in my raku kiln, the temperatures aren’t high enough to form a glaze although when I put an equal amount of borax in the newspaper twists I fill and dunk in water and throw in the kiln, it comes so close to making a glaze. But it induced immediate deep in kiln reduction, and has really interesting different effects on the glazes, bare clay, and slips on the ware that I love- and for one thing turns my copper luster pots blood red just perfectly, the only way I get really good looking “copper red” pots right now. I wonder if it would work on flashing slips at that low temp or not…no one has ever mentioned them when discussing lowfire or raku soda to me but I probably need to buy that new book that came out on lowfire soda firing. 

[ATauer]

On 7/30/2022 at 4:09 PM, Magnolia Mud Research said:

I have been using soda ash and/or baking soda solutions sprayed on areas of bisque and green ware for more than 10 years.  

The fired color surface depends on the clay body.
the appearance change of the fired surface is more a change in the value of the surface color of the fired clay body;   generally the color becomes more dark or stronger of the orange and yellow surfaces when treated with the soda application.  
a very white porcelain surface will show a faint graying in the white surface where the soda wash is applied.  
on a heavy iron clay body the surface will be darker where the solution was applied.  

I quit playing with "flashing slips" from any recipe and textbook about the same time I started spraying soda ash water;      instead, I spray the surfaces with the soda water and dust with various dry clays (kaolins  or ball clays) to greenware surface before the water soaks in; the soda water "glues" the clays to the surfaces and they may produce a crackled surface layer at the bisque and final firing steps.  sprayed areas with soda at bisque will show up with different values of the raw clays.  The amount of spray on an area is something that you develop yourself. 

I apply the soda -- get small spray bottles with a fine misting nozzle from the supermarket --- by spraying a little bit will make a change, a big amount will make a mess; somewhere in between is where you need to be; 
application by brushing requires careful not to get too much, you are not painting a house!   too much produces an area of "window glass glaze".  

The soda amount should be no more than 3/4 of the saturation amount; 
~1/2 saturation is about optimal.    I make my by adding soda to a bottle half full of water and when the soda quits dissolving I stop adding soda and fill the bottle with water.    Baking soda is easier to handle than soda ash; solubility charts for soda ash and baking soda are easily found in the manuals from the suppliers.  

location in the kiln is also an important variable along with any reduction variables;
fired in an electric kiln will also show effects, but they will be different than in gas or wood fired environment. once you find the "right spot" negotiate with the kiln operator to where you want your item located in the kiln.  

I have NEVER achieved a "greenish color" due to saturation of the surface with the soda;   once fired a cup that was soaked for three months in a soda ash solution; completely covered with soda ash crystals all over; it came out of the firing with a clear glassy coating -- similar to window glass, but no green; not very interesting either! 

applying "under a glaze" is the equivalent of adding soda to the glaze; that also goes to application over a glaze. exactly how much the soda changes the glaze recipe depends on the glaze application and the porosity of the bisque ware, and sometimes what you will have for dinner next week.  essentially the arrangement will be the same as two glazes overlapped. 
 
A final recommendation:  don't attempt to copy a color from an image in a book or from the computer as your target; spend your energy observing what you have available such as the clays and kiln firings, learn something about the materials you have already and the environments in the firing.  You will begin to make objects that no one else has nor can produce.  You will make the method your method.   

What started me down this rabbit hole was an attempt to make salt glazed wood fired ware in a college studio using the cone 10 reduction gas kiln without using salt or wood;   with some carefully application of baking soda, the right clay body, and some sea shells, the appearance was very close to salt/soda ware, fired with all the other studio ware, and the effort is no different than any normal glaze firing.  

footnote 1; for what it's worth: the right amount of soda added to kaolin can convert kaolin to Nepheline (not Nepheline Syenite) which starts to melt somewhere around cone 0; you can figure the ratios by looking up the composition of nepheline in a geology textbook.  this is one reason the method works.  

footnote 2: soda ash - the chemical name is sodium carbonate; baking soda - the chemical name is sodium bicarbonate.  limited chemistry data is available via wikipedia. 

footnote 3: adding other materials such as borax, and other materials moves the process away from soda to something else.  They may be useful, but the result is not what you asked about. 

LT

You said the right amount of soda and kaolin mixed starts to turn to a Nepheline around cone 0, while Nepheline Syenite when it starts to melt around cone 2 or 4 I think it is will end up on its own melting into a glossy glaze, it just crazes terribly because the amount of sodium in neph sye. I’m wondering if the Nepheline that forms around cone 0 with soda and kaolin would also form a glaze at around that temp or up to cone 06…which is how high I usually fire my raku kiln when I add soda ash to it. They always say at that temperature you can’t form any glazes, it isn’t hot enough, but they aren’t talking about the Nepheline, right? I’m probably groping in the dark here, I’m just wondering how I could use the fact that Nepheline is forming, which if it is close enough in chemistry to neph sye might form a glaze, even if it crazes, that wouldn’t be a problem with raku work. I’m just trying to figure out if I can use this new knowledge to produce something at cone 06….