Magnolia Mud Research

IMHO that really does looks like a bloat/bleb from an air bubble in the clay wall. When the glaze melts it seals the clay over so the gas can't escape and you get those bloats/blebs. 
After wedging your usual way try slicing a few chunks of clay up into thin slices and look for air pockets. Keep doing this until you can wedge without getting them. Try cut and slam wedging also if you don't already do this.
I'ld also suggest doing some absorption tests on your claybody given it is being fired below it's maturity, how to that here if you need it, about 2/3 the way down.

Something a little different just finished up in my studio this week!  'Smitten' medallion (small plaque) , sculpted by Rebecca Turner, produced in earthenware ceramic by Marge Para, and custom glazed by myself as a show donation for Clinky Mania Live 2024 in Titusville, FL this May.  All work done in the kiln using underglazes, then satin clear, followed by some overglazes to punch up the colors in the cat.  This ceramic medallion measures 3.5 by 5 inches and is going to public auction to benefit the show.    Photo displayed is MUCH larger than the actual piece!
I don't do many donation pieces anymore as I am just too busy but this is to help support a good friend's last year of hosting this show series for equine ceramics.  With all the heavy storms up here we've had in these mountains the past week it's been hard to fire either of my kilns with so many power outages and all the lightning.   But I finally got it done!  

I agree strongly.  India ink enhanced crazing can be very dramatic and beautiful.  If you or the gallery owner can't live with the result, the ink will burn off if you refire the piece.

Please do post an update on the re-fire...

Rub ink into the crackles and say, “I meant to do that”?

Great question, and as you see, there are reasons for different answers.  I dip all of my test tiles, so the are the same on both sides. Then I use small shot glass type testers to see if the glazes interact with each other in weird ways. . . . why the shot glasses?  Easy to throw off the hump, simulate a pot form and allows me to test inside and outside combinations. Finally if there are any weird interactions from different glazes that may cause the pot to crack, craze, shever or anything else, the shot glass shape is more stable and will keep the glaze from doing too much to the kiln. Lots of them can be fired as extras in any load.
 
best,
Pres

While I’m one of the first people who will usually say it’s a bad idea to sell crazed functional ware, why are concerned about crazing on sculptural work? Sculptures don’t have the same durability demands placed on them as dishes. They might have their own durability demands if they’re outside, but I digress.

Soldate 60 is great stuff. It's a cone 10 clay but for sculptural firing to midrange would work too. I've known people use it for Raku firing also.

If you are firing in the cone 10 range and these clay items are just sculpture then Laguna's WSO is the most forgiving clay I have ever found.I feel Bmix with grog is not your best sculpture clay no matter what temp range-get a more loose body
It's more like a cement feel than clay and very tough to crack. I made a 3 foot wall fish from it and it came out fine spanning 3 -12x24 kilns shelves on a waster slab

An interesting thought if you have never done any sort of pottery maybe take a course or two if possible, to see what you may like. Learning to build a gas kiln and operate it reasonably proficient - maybe a year or two. Learning and becoming  proficient in all aspects of pottery - maybe a lifetime.

Also make sure your bat pins are tight.

When we produce a ceramic material that allows "light" to pass through that material we are working with a "glass" even though us potters call the material a clay body or a glaze.  
Todays "Ceramic-Tech-Today"  article: Colored glass: From alchemy to empirical chemical design  
https://ceramics.org/ceramic-tech-today/education/colored-glass-from-alchemy-to-empirical-chemical-design/   
has some useful information and background that might help determining why the bone-china pots show a color when seen in a light source.  Remember that the source of the "light" is also an important variable.  
LT
 

When we produce a ceramic material that allows "light" to pass through that material we are working with a "glass" even though us potters call the material a clay body or a glaze.  
Todays "Ceramic-Tech-Today"  article: Colored glass: From alchemy to empirical chemical design  
https://ceramics.org/ceramic-tech-today/education/colored-glass-from-alchemy-to-empirical-chemical-design/   
has some useful information and background that might help determining why the bone-china pots show a color when seen in a light source.  Remember that the source of the "light" is also an important variable.  
LT
 

Probably. 
Part of the fun of working with found materials is the variability. Sometimes close enough is all that’s needed.

I make terra sig regularly with my local clay and follow something similar to @Magnolia Mud Research’s post. I don’t go to great lengths to extract any remaining “finest particles” from the dregs. I played with that a bit but found it was counterproductive.  Letting it slake a few hours then mixing it really well gets the all good stuff in suspension. 
I’m sure this is derived from Vince Pitelka or maybe Pete Pinnell, but it’s what I go with:
1 quart water to 1 pound of clay. 2.5 grams deflocculant per pound of clay.
My deflocculant is half soda ash/half sodium silicate. 

At 800 degrees, the glaze particles have not begun to sinter, they are just a little toasty. Fix the kiln and refire.

Your not alone there.
White is just about the first adjective I think of when bone china is mentioned. It's an interesting idea that it might really be objectively bluish but subjectively  "whiter than white" (like many detergents).

The change from "whiter than white" to a more visible greenish tint then doesn't seem so implausible. Possibly due to some subtle change in the nature of the glass in which the (iron?) chromophore is embedded.
From @Min's reference.

PS a test-tile without Veegum seems an increasingly interesting idea.
BTW how are small test-tiles for different body compositions usually made? Using volumetric mixing ideas from glaze tests would seem sensible if you need to do lots. Perhaps drying the over-wet samples on plaster or in plaster moulds - or applying as a slip to a biscuit tile (although that might make inspection more difficult).
PPS Can you confirm that you have observed the green tint under several different lighting conditions. So we can exclude any light-spectrum related issues (c.f. neodymium glass).

The two photos are from Luxurybonechina.com and narumi.co.jp. 
A link to another photo is here: https://simple.wikipedia.org/wiki/Porcelain#/media/File:Transparent_porcelain.jpg
I get the sense a greenish tinge to bone china is not so unusual. The green of the piece @Jarman Porcelain posted is tilted away from a yellowish I would expect from iron, but not so much to make me think iron’s not primarily responsible. The clay body is a hair’s breadth from being a glaze at maturity (the ultimate clay/glaze interface: the pot is the glaze). Grolleg and Standard both have over 0.5% iron in them, perhaps that’s enough to show when it’s all in the melt? NZK has half the iron of those two, so I don’t know.
I found this interesting, since I feel like I hardly know what I’m talking about: https://www.jonsinger.org/jossresearch/tjiirrs/017.html
I certainly imagine getting some into a reduction firing, being able to compare, would provide useful information. 

Do you think there is a link between the Veegum  and the bone ash or TCP? (Veegum being magnesium aluminum silicate) Interesting read here https://www.researchgate.net/figure/Concentrations-of-phosphorus-pentoxide-and-magnesia-in-Roman-emerald-green_fig1_277089354 possibly linking the two with a green colour.

I've been there.  and learned to ignore the "official methods" and simply crushed the dry clay as small as possible using a hammer and kitchen screen utensils to get rid of the "big" rocks.  
Mix the clay with water to make a slurry that is somewhere between the buttermilk and the milk level (or a little less).  Let the mixture set for a while to let the heavy particles to sink, and then pour the liquid into a separate container which will contain most of the sig.  Stir up the original container again and let it set a while, and repeat pouring off the water to get remaining sig. Yes, this is not the official method, but it has worked just fine for the clay I take from my ponds and roads to them.  I have also used that same method for making sig from scrap commerical clay bodies. 
If you are able to get wet clay from the backyard just start with that; add water and mix well; if you have sand, it will sink along with the heavy particles.  I have a pond that collects fine clay every time there is a decent rain. After the rain there will be a thin layer of fine clay above the big paricles.  My first round on terra-sigillata I followed the "official" method; it worked ok.  After noting what was happening in the ponds and just getting a bucket of pond mud and water I begin to make my own method which has worked just as good as the textbook. 
The best "official" recipe I have found (beyond my own) is Vince Pitelka's version:
http://www.vincepitelka.com/wp-content/uploads/2022/10/Super-Refined-Terra-Sig.pdf   
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I've been there.  and learned to ignore the "official methods" and simply crushed the dry clay as small as possible using a hammer and kitchen screen utensils to get rid of the "big" rocks.  
Mix the clay with water to make a slurry that is somewhere between the buttermilk and the milk level (or a little less).  Let the mixture set for a while to let the heavy particles to sink, and then pour the liquid into a separate container which will contain most of the sig.  Stir up the original container again and let it set a while, and repeat pouring off the water to get remaining sig. Yes, this is not the official method, but it has worked just fine for the clay I take from my ponds and roads to them.  I have also used that same method for making sig from scrap commerical clay bodies. 
If you are able to get wet clay from the backyard just start with that; add water and mix well; if you have sand, it will sink along with the heavy particles.  I have a pond that collects fine clay every time there is a decent rain. After the rain there will be a thin layer of fine clay above the big paricles.  My first round on terra-sigillata I followed the "official" method; it worked ok.  After noting what was happening in the ponds and just getting a bucket of pond mud and water I begin to make my own method which has worked just as good as the textbook. 
The best "official" recipe I have found (beyond my own) is Vince Pitelka's version:
http://www.vincepitelka.com/wp-content/uploads/2022/10/Super-Refined-Terra-Sig.pdf   
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Cobalt being v expensive I wonder if your glaze could handle less. 2% seems a high amount of cobalt oxide.
 

I use a plastic bowl for water . Its a wide open form -I keep a cut shammy on the lip and few sponges in it. I get fresh warm water every throwing day from electric tea kettle-my guess is 1/2 +gallon of water-less water the better in terms of throwing

Some time ago I posted about challenges with wollastonite clumping.  I have now found a process which is helping with this issue.  I utilize one of these flour sifters when weighing out the wollastonite.
  I sift the material directly into a pan on the balance until I have the necessary amount.  It's pretty low tech, but it works.  Perhaps not feasible for large-scale batches, but I'm usually making 1-2kg batches of most of my glazes, and it works fine for that.
 

I would make my own wash and remove with a wet sponge  before firing any commercial wash as it usually poor quality.
Speaking of quailty wash I noticed on the Advancer shelve (kiln shelve.com ) site they use the same formula as I posted years ago
1/2 alumina hydrate
1/4 epk
1/4 calcined EPK or (glowmax)