Min

Hi Hannah and welcome to the forum.
I've never used ash from domestic waste but your post has made me curious. I did a quick google search and found a fair bit of info on Municipal solid waste ash. From one study the main components found in it were Si, Al, Fe, Mg, Ca, K, Na, Cl, SiO2, Al2O3, CaO, Fe2O3, Na2O, K2O. But also found in the fly ash were the heavy metals, "Cr, Cu, Hg, Ni, Cd, Zn and Pb are the most commonly found in MSWI ash, and Zn and Pb usually exist in the largest amounts (fly ash and bottom ash..."
For a comparison a general generic analysis of wood ash from Hamer and  Hamer would be  8 Na2O, 17 K2O, 12 MgO, 27 CaO, 1 Al2O3, 24 SiO2, 7 P2O5, 4 Fe2O3
The heavy metals lead, cadmium and mercury found in domestic waste ash testing done in the link (below) I pulled this info from would be an area of concern. 
https://www.mdpi.com/2071-1050/2/7/1943

I think that since so many of us fire to midrange the go to mindset is bisque low, fire higher to glaze. Problem with this when working with earthenware is more often than not the commercial glazes are rated in the 06-04 range yet many earthenware bodies will actually mature higher than this and still be porous enough to take glaze well. I haven't used the body in question, but if it can go to 02 (as the lit suggests) then I would at least try 03 and see how it does. 

Small test kilns can fire incredibly fast, much faster than larger electric kilns. So yes, if the “real” pots will be fired in a larger kiln then you’ll want to approximate the same firing speed. I would suggest asking the studio where you fire your work what schedule they use plus how long the firing takes then program your test kiln to match it as close as you can. Test kilns also cool down super fast so you probably should do a slow cool down also. This wouldn’t be necessary for clear glazes though. 

Hi Hannah and welcome to the forum.
I've never used ash from domestic waste but your post has made me curious. I did a quick google search and found a fair bit of info on Municipal solid waste ash. From one study the main components found in it were Si, Al, Fe, Mg, Ca, K, Na, Cl, SiO2, Al2O3, CaO, Fe2O3, Na2O, K2O. But also found in the fly ash were the heavy metals, "Cr, Cu, Hg, Ni, Cd, Zn and Pb are the most commonly found in MSWI ash, and Zn and Pb usually exist in the largest amounts (fly ash and bottom ash..."
For a comparison a general generic analysis of wood ash from Hamer and  Hamer would be  8 Na2O, 17 K2O, 12 MgO, 27 CaO, 1 Al2O3, 24 SiO2, 7 P2O5, 4 Fe2O3
The heavy metals lead, cadmium and mercury found in domestic waste ash testing done in the link (below) I pulled this info from would be an area of concern. 
https://www.mdpi.com/2071-1050/2/7/1943

Small test kilns can fire incredibly fast, much faster than larger electric kilns. So yes, if the “real” pots will be fired in a larger kiln then you’ll want to approximate the same firing speed. I would suggest asking the studio where you fire your work what schedule they use plus how long the firing takes then program your test kiln to match it as close as you can. Test kilns also cool down super fast so you probably should do a slow cool down also. This wouldn’t be necessary for clear glazes though. 

I looked up the Mass Red clay from Sheffield Pottery, from their info it fires from 06 up to 02. I don't use commercial glazes so I also looked up the glazes you are using, Mayco Elements have a range from ^06 up to ^6 and the opalescent are ^05 if you go at 270F and hour for the final 200F of firing and the Artist's Choice recommend ^05. 
All claybodies are strongest when fired to their top maturity temp/cone. So for your body the clay needs a higher bisque than what your glazes fire to. This is okay for earthenware as the body will still be porous enough to accept the glaze well. I would suggest bisque firing to ^02 and turning the dial up very slowly. Don't rush when you turn it up! Leave  peeps open to get air through the kiln, it helps burn off impurities in the clay. I would suggest leaving all the peepholes open until you see the kiln glowing red inside then shut the bottom one and leave the top one open for the entire firing. Once the kiln stops then you can close the top one off. (I'm assuming it has 2 peepholes?)
For the glaze firing, again you want to slow it down, doesn't have to go as slow as the bisque though. I'm not familiar with your kiln but what you are trying to do is slow down the firing, Try and stretch out the middle and then particularly the end of the firing. Someone more familiar with your kiln than I am should be able to help you with this part. 
Given that the clay has already reached it's maturity with the bisque firing then the glaze firing is to get the best looking glazes you can. Cone 05 should do it although the Mayco Elements can go higher, if you have a hotter area in your kiln you could try putting those glazes there. When I looked at some images of Mayco Elements I do see a fair number of pinholes in one of them when fired to ^06 so the odd one might be more prone to pinholes. (image below from Mayco's website of Oyster Shell)
 
 

Small test kilns can fire incredibly fast, much faster than larger electric kilns. So yes, if the “real” pots will be fired in a larger kiln then you’ll want to approximate the same firing speed. I would suggest asking the studio where you fire your work what schedule they use plus how long the firing takes then program your test kiln to match it as close as you can. Test kilns also cool down super fast so you probably should do a slow cool down also. This wouldn’t be necessary for clear glazes though. 

For sure you can get the chem to match using silica + calcium carb for wollastonite. I've done the reverse with recipes calling for calcium carb and subbed in wollastonite and reducing the silica in the recipe so the formulas match. What I found was the wollastonite versions melted noticeably more.  Some recipes won't show a difference, depends on glaze mobility and how much CaO is involved. I think another factor is the mesh size of the silica being used in the recipes. Perhaps very fine silica, ie 90 micron compared to 45 micron would show a difference in the melt if used with calcium carb? I've always thought of wollastonite as being like a frit, albeit a lumpy one, it melts really well and with minimal LOI.

For sure you can get the chem to match using silica + calcium carb for wollastonite. I've done the reverse with recipes calling for calcium carb and subbed in wollastonite and reducing the silica in the recipe so the formulas match. What I found was the wollastonite versions melted noticeably more.  Some recipes won't show a difference, depends on glaze mobility and how much CaO is involved. I think another factor is the mesh size of the silica being used in the recipes. Perhaps very fine silica, ie 90 micron compared to 45 micron would show a difference in the melt if used with calcium carb? I've always thought of wollastonite as being like a frit, albeit a lumpy one, it melts really well and with minimal LOI.

Is this the commercial Amaco  Wash you are using? If it is I would try brushing it on the wiping it back with a damp sponge to remain in the recesses then apply a glaze over top. I think leaving it without wiping it back would be too intense. Whatever glaze you use will dilute the intensity of the Amaco Wash.
 

I guess it would depend on whether the data on Glazy is the same as someones current material analysis (garbage in garbage out). Materials data fields vary between sources.

Is the glaze coming off during the firing and landing on the kiln shelf? If that is the case, it can be due to the way the wet glaze dries and cracks and falls off.
If the glaze is not falling off onto the shelves, but is leaving bare spots, that can be a different cause.
I can't tell which is happening from the description or photos.

If the food colouring is just to tint the raw slip then I would suggest using paste food colouring rather than the liquid, it goes much further.

Claybodies should be vitrified enough to not weep / leak even with no glaze on them when used for functional work and fired to mid or highfire.
Is this the clay you used? https://tuckers-pottery-supplies-inc.shoplightspeed.com/mid-smooth-stone-speck-clay-cone-6-stoneware-ecom.html
If that is the clay then in theory the clay should be vitrified enough to not leak with a posted absorption figure of 1.0 % but published figures can vary by +/- 1%. I would suggest running your own absorption tests. This is a good idea to to when using a new clay or every once in a while on an existing clay as materials can change.
How to on testing for absorption here if you need it, about 2/3 the way down the page, I would suggest doing the weight calculation test with several samples placed in different areas of the kiln. 

If she isn’t absolutely 110% sure it’s a cone 10 clay then I would pass on this. 
This makes sense to fire the clay to maturity / cone 10 if she doesn’t plan on glazing it and it is indeed a cone 10 clay. She might want to leave it as bare clay or be planning on doing a cold finish on it. Firing to maturity would be a clearer way to describe what she wants rather than calling it a bisque firing. A mature body is far stronger than a bisque fired body.

Slow. Both for firing up and cooling down.
These pictures are from Digitalfire of lowfire ware, pots have cracked from uneven cooling, edges will have cooled faster than the middle area of the pieces. The way to avoid this is to have the cooling down go as evenly as possible. Slow the cooling down between 1150F - 950F, I go at 100F/hour through this zone with suspect work.

 There is negligible shrinkage, ie less than 1% between bone dry greenware and bisque firing to ^06- ^04, would be interesting to see data that shows refiring to a lower temp causes more shrinkage.
edit: when having your piece in the kiln put it between shelves, not at the top or bottom of the kiln, this helps the heat even out also. I put rectangular or triangular kiln posts around the outside edge of the shelf also. (round posts can roll)
 

If it hasn't been fired on yet then yes it can be dusty. 
It would just be a guess but the least expensive materials to use in a kiln/ batt wash would be kaolin and silica so if companies are trying to save money with the wash they supply they will load the wash up with that and skimp on alumina hydrate. There is a link below discussing kiln/batt wash with some tried and true recipes (it's towards the end of the link). Also, I would suggest wiping it back from the edge about 1 cm and wipe off any drips from the side of the shelf.
https://community.ceramicartsdaily.org/topic/20981-frit-substitution-chart-orton-cone-charts-kiln-wash-recipes/

If it hasn't been fired on yet then yes it can be dusty. 
It would just be a guess but the least expensive materials to use in a kiln/ batt wash would be kaolin and silica so if companies are trying to save money with the wash they supply they will load the wash up with that and skimp on alumina hydrate. There is a link below discussing kiln/batt wash with some tried and true recipes (it's towards the end of the link). Also, I would suggest wiping it back from the edge about 1 cm and wipe off any drips from the side of the shelf.
https://community.ceramicartsdaily.org/topic/20981-frit-substitution-chart-orton-cone-charts-kiln-wash-recipes/

I see that there are some cracks running from one lump to another.  I make a lot of tile,   a thicker area next to a thinner slab can cause cracks to form.   She might try removing the clay from the back of the tile in the thick areas  and try to keep the clay a even thickness.  Denice

Slow. Both for firing up and cooling down.
These pictures are from Digitalfire of lowfire ware, pots have cracked from uneven cooling, edges will have cooled faster than the middle area of the pieces. The way to avoid this is to have the cooling down go as evenly as possible. Slow the cooling down between 1150F - 950F, I go at 100F/hour through this zone with suspect work.

 There is negligible shrinkage, ie less than 1% between bone dry greenware and bisque firing to ^06- ^04, would be interesting to see data that shows refiring to a lower temp causes more shrinkage.
edit: when having your piece in the kiln put it between shelves, not at the top or bottom of the kiln, this helps the heat even out also. I put rectangular or triangular kiln posts around the outside edge of the shelf also. (round posts can roll)
 

@MsBeth, for the fondant molds are you using flexible silicone molds? 
I think there is a bit of confusion with the terminology being used, when you say "clay castings" is seems like you are using casting slip. But then "press the clay into the mold" sounds like you are using pugged soft clay. 
I have used flexible silicone molds and soft clay, I very lightly wiped the molds with veg oil then pressed the clay in then flexed the mold enough to have the clay pop out. There was a bit of distortion with the molds with undercuts but it was easily fixed since the clay was soft. 
Dusting molds with cornstarch is also an option, don't have to be concerned with airborne silica with it.
Welcome to the forum.
 

If she isn’t absolutely 110% sure it’s a cone 10 clay then I would pass on this. 
This makes sense to fire the clay to maturity / cone 10 if she doesn’t plan on glazing it and it is indeed a cone 10 clay. She might want to leave it as bare clay or be planning on doing a cold finish on it. Firing to maturity would be a clearer way to describe what she wants rather than calling it a bisque firing. A mature body is far stronger than a bisque fired body.

If she isn’t absolutely 110% sure it’s a cone 10 clay then I would pass on this. 
This makes sense to fire the clay to maturity / cone 10 if she doesn’t plan on glazing it and it is indeed a cone 10 clay. She might want to leave it as bare clay or be planning on doing a cold finish on it. Firing to maturity would be a clearer way to describe what she wants rather than calling it a bisque firing. A mature body is far stronger than a bisque fired body.

The concave then convex side design might also be contributing to it being pulled out of round. 

The concave then convex side design might also be contributing to it being pulled out of round.