PeterH

Hi Dot,
Welcome to the Forum!
Crazed wares, almost certainly weaker*, and liquids can be a concern, particularly where the fired clay's absorption rate is "high"...
For sculpture (and other non-food ware), however, crazing may be ok?
Reversing crazing, that may not be possible.
My understanding is that crazing occurs when the clay and glaze COE** are different enough, and that can only be corrected by changing the glaze and/or clay.
If the clay matures at a higher cone (than 04, in your case), the fit may change when fired higher, but not necessarily a better fit!
Check back for more responses...
 
*A well fitted glaze makes for stronger ware
**Coefficient Of Expansion
Co-efficient of Thermal Expansion (digitalfire.com)
see also Mr. Hansen's articles on glaze crazing, glaze fit, glaze compression 

I haven't seen that, and would be interested if you have a ref.
But I have seen occasional references to needing to let the pot dry sufficiently between glazing one surface and the other.
... this seems to be more of an issue with dipped glazes than painted ones.

Good find Peter.
When I look at the analysis for both there are other differences too though. Definitely a fragile mechanism to get the green. Reitz Green with Gillespie doesn't need the lithium carb and dolomite additions when I played around with altering the recipe, the silica is a tiny bit higher in the Gillespie version but given the differences in the Floating Blue recipe that might or might not be consequential, I don't know. 
A simple addition of iron with a reduction of cobalt would be simple to test Hansen's theory if it translates to Reitz Green also. I suppose RIO would be the logical material to add as long as speckles don't become an issue. Or black iron oxide might be better if you have it. 

Any relevance?
https://digitalfire.com/material/gerstley+borate
... at the bottom of the page, discussing substituting  Gillespie Borate  for Gerstley Borate ...
Clearly, the Floating Blue itself is firing greener than usual. And the Gillespie Borate version is much bluer. You may be used to something in between these two. The green tones could likely be restored by a reduction in the cobalt and increase in the iron oxide.

Any relevance?
https://digitalfire.com/material/gerstley+borate
... at the bottom of the page, discussing substituting  Gillespie Borate  for Gerstley Borate ...
Clearly, the Floating Blue itself is firing greener than usual. And the Gillespie Borate version is much bluer. You may be used to something in between these two. The green tones could likely be restored by a reduction in the cobalt and increase in the iron oxide.

Re-reading Digitalfire the second paragraph seems relevant..
Glaze Shivering
https://www.digitalfire.com/trouble/glaze+shivering
Shivering is the opposite of glaze crazing, the fired glaze is under compression and wants to flake off the body, especially at edges. However the route cause is a mismatch in the thermal expansions of body and glaze, thus the process of resolving it is similar as for crazing. It it much less common because glazes tend to have a higher thermal expansion than bodies and because they can tolerate being under compression much better than being under tension. Of course, if a glaze is under compression on the inside of a vessel, the body will be under tension and this can cause failure of the piece.
When the body-glaze interface is not well developed an overly compressed glaze will be able to release itself much more easily, especially on the edges of contours. This can be the case, not only with low fired ware, but where engobes or slips are being used under the glaze. If the engobe does not contain enough flux to firmly adhere it to the body and develop hardness, it will not be able to bond to the glaze well.
PS Time for some rim-shaped test-tiles?

It would be nice if you started a thread on the topic in say 3-12 months indicating your successes and failures in this area.
PS A less well-known technique to achieve reduction. Which I think I've only seen mentioned in a 1932 paper on copper reds.
 

Shivering is generally considered a clay body problem, the exception being one glaze out of many that shivers while the rest fit.
With slip (the added kaolin is not helping), underglaze, and glaze, you’re working on making four things play nice. If you’ve dropped the slip, you've narrowed it down.
The application and gum are unlikely to be the source or solution of your problem. Adhesion at room temperature counts for very little in this equation. It’s the clay bodies. Wildly different coefficients of expansion from either the glazes or the underglazes. Continue eliminating variables, you’ll solve it. 

Thanks Peter for the links! I actually have been thinking about exploring slow cooling as well as putting things in saggars to get reduction effects.  I am sure I can figure out ways to get glazes I like in an electric kiln… just won’t be quite as straight forward as doing it in a gas kiln…

If you are leaning that way have you explored slow-cooling in an electric kiln? Which can have a dramatic effect on some glazes.
PS Some eye candy.

https://ceramicartsnetwork.org/daily/article/Super-Cool-Slow-Cooling-in-an-Electric-Kiln

 
https://cone6pots.ning.com/forum/topics/slow-cooling

 
https://ceramicartsnetwork.org/daily/article/Tips-for-Increasing-or-Decreasing-Crystallization-in-Glazes
... same glaze fired in a gas kiln: with the "natural" slow cooling of a gas kiln & with a "crash" cooling similar to that usually given by an electric kiln.

https://digitalfire.com/schedule/c6dhsc
https://digitalfire.com/picture/bestenazoh

https://digitalfire.com/picture/3348

 
A  discussion on iron reds in this thread
http://ralpotterystudio.blogspot.com/2010/08/new-glaze-tests-710.html
... a fairly mixed bag, including

Previous firings of this glaze at cone 6 or less without slow cooling produced dark browns. This is one that really requires slow cooling to get the red appearance, but proves you can get red reds at cone 6.

If you are leaning that way have you explored slow-cooling in an electric kiln? Which can have a dramatic effect on some glazes.
PS Some eye candy.

https://ceramicartsnetwork.org/daily/article/Super-Cool-Slow-Cooling-in-an-Electric-Kiln

 
https://cone6pots.ning.com/forum/topics/slow-cooling

 
https://ceramicartsnetwork.org/daily/article/Tips-for-Increasing-or-Decreasing-Crystallization-in-Glazes
... same glaze fired in a gas kiln: with the "natural" slow cooling of a gas kiln & with a "crash" cooling similar to that usually given by an electric kiln.

https://digitalfire.com/schedule/c6dhsc
https://digitalfire.com/picture/bestenazoh

https://digitalfire.com/picture/3348

 
A  discussion on iron reds in this thread
http://ralpotterystudio.blogspot.com/2010/08/new-glaze-tests-710.html
... a fairly mixed bag, including

Previous firings of this glaze at cone 6 or less without slow cooling produced dark browns. This is one that really requires slow cooling to get the red appearance, but proves you can get red reds at cone 6.

If the SG was 1.36 to start with but seems thinner now it's probably just because some of the solubles in the glaze deflocculating it.

I calculate  240/17.3 + 240/(8.6+8.6) + 240/17.3 = 41.7 amps
I'm not familiar with kilns, but the difference between 40 & 41.7 could well be related to the fact that the resistance of the elements rises as they get hotter.

PS There are lots of mnemonic diagrams about if you need a reminder of the formulae.
https://duckduckgo.com/?q=voltage+current+resistance+triangle&t=ftsa&iax=images&ia=images

Purely as an example, you can find Paragon kiln diagrams at
https://corp.paragonweb.com/support/kiln-wiring-diagrams/
There are three for the TNF233 (single/three phase and probably different controllers), showing differences in resistance and connectivity between elements.
e.g. https://eadn-wc04-7751283.nxedge.io/wp-content/uploads/Wtnf233.pdf
BTW what is your mains supply?
https://en.wikipedia.org/wiki/Mains_electricity_by_country
Nominal voltage is 230/400 V, in practice 240/415 V is more commonly used.
 

A picture of one of Carlton's horns, and other peoples work (e.g. 4-headed drum, multi-chambered wind instruments, ...)
clay musical instruments
https://www.pinterest.com/baldaufa1/clay-musical-instruments/

Suspending the handle with wires is a far more complicated way to do it and just using more oil clay to lay in a bed complete with keys.  Pour one side in plaster, then flip it all over, remove the oil clay bed from the handle, then pour the plaster on the second side.  Very easy.
That said, I'd suggest you sculpt the handle you want and get us a photograph both of the handle at a few angles and how you think you want to set it up in your mold box.  Much easier for folk to help you if we have visuals.  Otherwise you already got lots of great advice here.

I think that you will find this difficult. It's more usual to use some sort of clay "build-up" to keep the plaster under control, as in
PS A handle is nice and thin so there is no difficulty using a solid clay build-up.  For larger objects you may want to minimise the amount of clay used for the build-up.
e.g. https://youtu.be/pXQgi6vW22I?t=698
To state the obvious: bits of plaster can explode in the kiln, so keep any clay used for mould-making well away from the clay you use for making pots. 

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. 

It's rate to just above cone 6, which means it'll only get to cone 6 maybe 50 times max before the elements need to be changed.  Probably a lot less than that given the quality of the elements they are likely using. So to get any sort of real life from the elements you'll probably want to limit this to cone 2 at the most. Really we consider cone 6 kilns to be best suited for low fire work. I would definitely check to see if you can even get replacement elements for it.
It appears to be on angle iron legs, but they're not very tall. Most kilns have 8" legs, so this kiln is on the short side and it should definitely need to be placed on something fireproof. If it were mine, I wold put it higher up on some bricks to give more air flow under it, with a fireproof floor below.

Some plausible-looking advice on techniques and H&S referenced in:
Historically there have been two sorts of lustres: reduction lustres and resinate lustres. Your comments seem to apply more to the reduction-fired reduction lustres. While tho commercial oxidation fired products are resinate lustres.
Ever wondered why solder is often sold with a rosin flux running through it? When you apply it to the joint the hot rosin reacts with any oxide on the copper surfaces to form copper resinate.
The resinates lustres are made by reacting metal oxides or salts with rosin and dissolving the resinate in  or another solvent. With luck you finish up with quite a high concentration of metal resinate  in the solvent. When these are fired they decompose leaving a thin metal film (and often some pretty nasty fumes).
As Min said, do try and get in touch with @liambesaw if you can, but he hasn't visited the here since  2022.
A friend used to run a garage industry making resinates and had very strong reservations about many of the solvents used in commercial lustres, sticking to - AFAIK - linseed oil.
Manufacture a gold lustre is fairly briefly covered in "Pottery Decorating" by R. Hainbach.  Which involves mixing "bright gold" with a bismuth lustre. Bright gold apparently containing resinates of gold and rhodium (and also possibly bismuth, uranium, chromium and iron?). Although a simpler wet process is also described for producing gold resinate from gold trichloride and resin-soap.
... probably much better to find out what people do nowadays.
PS The book seems fairly expensive at the moment, change this search to your location and currency.
https://tinyurl.com/2d783cv8
 

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).

Some plausible-looking advice on techniques and H&S referenced in:
Historically there have been two sorts of lustres: reduction lustres and resinate lustres. Your comments seem to apply more to the reduction-fired reduction lustres. While tho commercial oxidation fired products are resinate lustres.
Ever wondered why solder is often sold with a rosin flux running through it? When you apply it to the joint the hot rosin reacts with any oxide on the copper surfaces to form copper resinate.
The resinates lustres are made by reacting metal oxides or salts with rosin and dissolving the resinate in  or another solvent. With luck you finish up with quite a high concentration of metal resinate  in the solvent. When these are fired they decompose leaving a thin metal film (and often some pretty nasty fumes).
As Min said, do try and get in touch with @liambesaw if you can, but he hasn't visited the here since  2022.
A friend used to run a garage industry making resinates and had very strong reservations about many of the solvents used in commercial lustres, sticking to - AFAIK - linseed oil.
Manufacture a gold lustre is fairly briefly covered in "Pottery Decorating" by R. Hainbach.  Which involves mixing "bright gold" with a bismuth lustre. Bright gold apparently containing resinates of gold and rhodium (and also possibly bismuth, uranium, chromium and iron?). Although a simpler wet process is also described for producing gold resinate from gold trichloride and resin-soap.
... probably much better to find out what people do nowadays.
PS The book seems fairly expensive at the moment, change this search to your location and currency.
https://tinyurl.com/2d783cv8
 

I would go back to square one and change just one variable at a time.
Original recipe of 50 bone ash (one test with real and another with TCP) 25 Cornwall Stone (if @Jarman Porcelain doesn’t have any I think I have a small amount left that I can share) and 25 kaolin (grolleg). Mix that up dry then  split into two and mix one batch with tap water (after flushing the tap for a few minutes) and the other batch with distilled water.
At the same time I would run the same two tests with Veegum included.
If these test show no green (or far less) then the field is narrowed down to something in the Cornwall sub being used.
 

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).

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).