Jeff Longtin

I think Roberta has the better suggestion. The depth of the fabric makes it very challenging to plaster. Rather than have that challenge just roll the fabric into a soft clay slab first and see if you like that. 
 

What about making a bisque mold of the fabric?  Roll the fabric into clay, dry and bisque, then make a plaster mold?  That would work if you are trying to get the texture of the pillow.    You could even drape the clay over the pillow to get the shape, roll the clay into the pillow and peel it off, retaining not only the texture but you could manipulate the clay to keep the shape of the pillow.  Just an idea.
 

Hello Vika,
It would appear that this is fabric, correct? In that case you need to seal the material before casting. A spray urethane would be best for that. You would probably need to apply several coats. 
Apply the urethane thick enough so you see a glossy reflection. That will tell you the fabric is sealed. 
Murphy's oil soap only works on porous materials like plaster or wood. 
As there appears to be many undercuts you may run into problems with the plaster getting stuck in the crevices. A simple way to seal those holes would be to apply a thin coat of plaster and then wipe the fabric with a sponge BEFORE the plaster sets up. Allow that layer to dry (30 minutes) Then apply a thin coat of Murphy's to the surface.
This will be a difficult thing to mold. Be prepared for a few challenges.

Jeff. I will pay attention to the grog additions, as I really dont measure, just kind of sprinkle. As for the water usage, I see where that would cause shrinkage/cracks also. If I ever get this problem resolved, I will post pics of my work without the hideous cracks! Thanks everyone

If we can take the firing issue off the table we're left with process. Two thoughts: 1) how much grog have you used? You may have too much in the clay, and 2) water- do you throw with lots of water? Perhaps the clay is getting too wet, in the throwing process, and its causing this shrinkage/cracking?
The other thought: to pick un on the Pres point, are you spending a lot of time trimming the pot? Making three rings must take awhile? Perhaps too much contact with the trimming tool. Have you tried not trimming the pots with a tool? (Leave them unfooted in other words.) Maybe use a trimming stick on the wheel and leave it at that.

Hello JJ,
In my experience reclaimed casting slip is not like new casting slip. Castings come out thicker and they take more time to set up. (The clay also tends to stay soft much longer.) As a result I try to mix my reclaim with new whenever possible. (50-50 isn't bad but 25% reclaim and 75% new is much better.)
Trying to cast pots with reclaim slip and expecting it, to be like new slip, only leads to frustration. (Been there done that.)
Knowing the kind of clay you have would help greatly.  All three clays, porcelain, stoneware, and earthenware, need to be deflocculated, but they can be deflocculated with different substances.  Darvan 7 is common for porcelain, but sometimes  sodium silicate is still used when manufacturers want to save money.  Soda ash can also be used.
Generally speaking I don't add deflocculant to reclaim. (As its already in there.) But different clays respond differently.
Your specific gravity at 1.68 is good. It indicates you should have enough water in your slip.  However the gel state could indicate a need for more deflocculat but before I suggest that more info would help.
 
 

As this just came out of the kiln I thought I would share: these are cone 6 porcelain casting slip test tiles.  (Coasters cut in half.) To which I've added various amounts of Mason Stains: Vivid Blue, Delphinium Blue and Zircopax. 
So that I can apply the glaze thinly I add stain to the clay, as well, to add to the opacity of the glaze. (I find that glaze drips/overlaps, become less evident if the clay body matches the glaze.)
Rather than use a total amount of 6% Vivid Blue, in the glaze, on top of a very white porcelain body, I added 3% to the body and 3% to the glaze. 
Its been a tedious process but its really interesting to see how the stains interact with the clay and glaze.

As this just came out of the kiln I thought I would share: these are cone 6 porcelain casting slip test tiles.  (Coasters cut in half.) To which I've added various amounts of Mason Stains: Vivid Blue, Delphinium Blue and Zircopax. 
So that I can apply the glaze thinly I add stain to the clay, as well, to add to the opacity of the glaze. (I find that glaze drips/overlaps, become less evident if the clay body matches the glaze.)
Rather than use a total amount of 6% Vivid Blue, in the glaze, on top of a very white porcelain body, I added 3% to the body and 3% to the glaze. 
Its been a tedious process but its really interesting to see how the stains interact with the clay and glaze.

I certainly didn't think glazing the pieces would be so complicated. I thought about spraying the glazes, for uniformity, but that too has complications.
Here's another photo showing more color tests.  Each of these test tiles represents a Mason Stain that no longer is being produced. The far left tile features Robins Egg 6 with Delphinium 2. The next tile is Delphinium 1.6 with Zircopax 8.4. The intense blue is Delphinium at 3.5% and Zirco 2. The purple tile is an attempt at the Violet and Amethyst. (6001 Pink with Vivid Blue)
The two yellowish tiles represent Peach. (6001 with Praesadium Yellow.)  
Note:  Many years ago Mason sold over 200 different stains. Today they sell 80-90. (guessing) They decided the world probably doesn't need to 10 different types of purple. What they did, instead, is to post the recipes for those discontinued colors on their website. ("Archived Formulas") Its tedious buying several stains, to produce one, but it does lead to some surprising color variations.

Probably because zinc can kill certain underglaze or mason stain colours, so it tends to be a go-to recommendation. To my knowledge, black isn’t one of the affected colours though. 

I picked up a little Evenheat test kiln last Fall and finally got around to getting it up and running this week. It was in brand new condition, only fired a handful of times to low fire temps, but it was a cone 8 kiln, not ideal for all the cone 6 firings I'll be doing in it. So I talked with Euclids and had them make me some custom elements that bumped it up from 2000 watts to 2700 watts, a 35% increase in power. It should have great element life now. It was originally set up for 120V service at 17 amps, and with the new elements it's set up for 208V 1P service at 13 amps (wired in series). I gutted the control box, removing the Kiln Sitter and wiring, and installed a terminal block that connects the elements directly to the power cord. I don't need the sitter since I'm using a wall mounted digital controller. The controller has a Genesis Mini controller and a solid state relay- you can see the heat sink on the left side of the control box. I've been using this box for a few years now and it works great. It was originally an Orton Auto-Fire, but I modified it a couple of years ago to work with the SSR. I also put the thermocouple in a protection tube.
I had a successful bisque firing yesterday, and I'm running a cone 6 glaze firing today. I don't expect any problems, but it's still a bit stressful since it's a new setup. Fingers crossed!

jeff.   thank you for clarifying my clumsy attempt to say the same thing.  some days are better than others and today was not a good one.

I'll pick up on what Hyn Patty says: some of us started making molds before the internet and we really only learned from our mistakes. In theory plaster is inert and should behave the way we expect it to.  Unfortunately that is not always the case and you need to improvise. That's when new ideas are born and new methods created. Continue your trials and feel free to post questions when they arise.
 

An alternative solution: if thinning the slip doesn't help you might consider making the pour hole larger OR adding a second pour hole altogether.  
Years ago I made a mold of a Vanhool bus model. (I also made the model.) The mold was about 22" long and 8" square. I put one pour hole, at each end,  to prevent a vacuum.  Wouldn't you know the customer emptied it sideways and created a vacuum. When they called to complain I explained that the two pour holes were intended to prevent such a thing. They changed their method and all was well.

Hello Handy,
Not quite sure why this is happening to you. When the "unexpected" happens to me I just roll with it. Rather than try to figure out why this is happening I would simply use this first casting as a "throw away" mold and continue pouring the mold. 
When you pour the second half it will likely go beyond half way and may hold onto the piece. In this case I would take a small trimming tool and carve back the plaster. (to the line you indicated/prefer)
Generally speaking I do not pour molds off clay.  (as the embedding material) If the form is complex I may use clay for that first pour but once plaster is poured I use that as the embedding material. (And discard the piece that was poured against clay.) This way I can more easily control the parting line and create a mold with nice tight seams.

Interesting fact: once a plaster form has thoroughly dried, after the initial pouring, re wetting it, and allowing it to dry a second time, will completely open the pores contained within. This is probably inconvenient, regarding a wedging table surface, but it would enable you to take the utmost advantage of the plasters aborbing capabilities.
The degree to which the plaster slab no longer can absorb water is dependent upon the clay you use. If your clay contains soluble salts, sodium silicate or barium carbonate, for instance, it may slow down with age, but most likely your clay doesn't so you can expect many years of use.  
As for drying a plaster form: heat is good but air movement is better. Too much heat, above 120 for instance, can start the breakdown process, too much air movement, has no bad impact at all. Put a fan on your plaster slabs and they should dry much sooner than simply letting the still air dry them. 

I'm not a chemist but it seems the salts move through the mold and accumulate on the surface. Washing the plaster might help but sanding the surface, and actually removing the salty buildup, would be more beneficial. (People who slip cast a lot have told me this.)
Drywall sanding screen is a wonderful way to take plaster down easily and quickly. (Though it is kind of messy.)

Brilliant:) thanks so much! 

Interesting fact: once a plaster form has thoroughly dried, after the initial pouring, re wetting it, and allowing it to dry a second time, will completely open the pores contained within. This is probably inconvenient, regarding a wedging table surface, but it would enable you to take the utmost advantage of the plasters aborbing capabilities.
The degree to which the plaster slab no longer can absorb water is dependent upon the clay you use. If your clay contains soluble salts, sodium silicate or barium carbonate, for instance, it may slow down with age, but most likely your clay doesn't so you can expect many years of use.  
As for drying a plaster form: heat is good but air movement is better. Too much heat, above 120 for instance, can start the breakdown process, too much air movement, has no bad impact at all. Put a fan on your plaster slabs and they should dry much sooner than simply letting the still air dry them. 

Interesting fact: once a plaster form has thoroughly dried, after the initial pouring, re wetting it, and allowing it to dry a second time, will completely open the pores contained within. This is probably inconvenient, regarding a wedging table surface, but it would enable you to take the utmost advantage of the plasters aborbing capabilities.
The degree to which the plaster slab no longer can absorb water is dependent upon the clay you use. If your clay contains soluble salts, sodium silicate or barium carbonate, for instance, it may slow down with age, but most likely your clay doesn't so you can expect many years of use.  
As for drying a plaster form: heat is good but air movement is better. Too much heat, above 120 for instance, can start the breakdown process, too much air movement, has no bad impact at all. Put a fan on your plaster slabs and they should dry much sooner than simply letting the still air dry them. 

Interesting fact: once a plaster form has thoroughly dried, after the initial pouring, re wetting it, and allowing it to dry a second time, will completely open the pores contained within. This is probably inconvenient, regarding a wedging table surface, but it would enable you to take the utmost advantage of the plasters aborbing capabilities.
The degree to which the plaster slab no longer can absorb water is dependent upon the clay you use. If your clay contains soluble salts, sodium silicate or barium carbonate, for instance, it may slow down with age, but most likely your clay doesn't so you can expect many years of use.  
As for drying a plaster form: heat is good but air movement is better. Too much heat, above 120 for instance, can start the breakdown process, too much air movement, has no bad impact at all. Put a fan on your plaster slabs and they should dry much sooner than simply letting the still air dry them. 

Metallic Glazes - Amaco makes two Potters Choice glazes that I have used. Gold Lustre - which looks like bronze metal, but not gold, unfortunately, and Palladium - this actually looks like Palladium/chrome when it fires successfully.  It is not food safe but it is safe for you to use in the studio. (though firing in a well ventilated area is best.) 

Yes it’s definitely not as bad as Bill’s pictures that’s for sure! It has a protective ceramic tube inside the kiln and when I pulled it out I did remember thinking the weld looked a little funny. This wasn’t based off of thermocouple knowledge, but just a bit of regular welding I’ve done in the past (basically all bad welds… ha). I didn’t take any of the tube sections off to check past the tip, but I figure a thermocouple is only $45 and this kiln is likely older than me and I’m not sure how many times it’s been fired so I may as well go ahead and replace it. 
It’s definitely 14gauge and I found a 5” one on evenheat’s website that seems to be about the same, but the block is different. All the ones that are sold now have the oval base like in Bill’s picture, but mine has a square block. I’ll attach a picture of how it’s mounted to the kiln. I’m thinking I may just have to remove the thermocouple from the new block and rewire it to mine? 
 
Y’all have been awful helpful and I thank you! I’m about to do a big project that would be too big for the studio I go to so this kiln is going to be getting a good workout once it’s fixed up. 

The bent TC is standard on a lot (all?) Evenheat kilns. They way they mount them is very solid, and the bend doesn't affect the performance.
@Bill Kielb I found one here in my shop and it's not 8 gauge. It measures out to be 14 gauge, which is why it can be bent like that. Beads only measure about 1/4" across and the protection tube is much smaller than what you'd find in an L&L or ConeArt.

I've been looking at lots of thermocouples this week. We have 18 kilns and I thought the prev kiln person was checking thermo's but it appears he was not. The Skutt's are easy enough to see the L&L Davinci's are less so. (Enclosed ceramic tube.) So I spent some time pulling out tubes and inspecting things. 
While your photos are good its hard to tell the true state of your thermo. Bill's pictures show the extreme end of thermo wear. The kiln manufacturers suggest replacing thermo's after 60 firings. In our case thats about 3 months. (At the pottery shop new kilns become "glaze kilns" and are fired, every day, to glaze temps.) We only honor the 3 month rule when the kiln is firing slowly or giving odd readings. Otherwise 4-5 months isn't bad. When the thermo has reached the stage pictured it's definitely time to replace.
Another example of an old thermo is a bloated end. Rather than seeing two rods welded at the end it appears to be two bloated wires side by side. (With a bloated/bulbous tip.) This was the case this week. I saw lots of bloated tips. While the thermo works the kilns are taking longer than expected and some of them are seeing greater-than-normal temperature variations.
Additionally, Bill's other picture shows a thermo as they typically are set. Straight, with a ceramic block that holds the wires and the thermo together. I've not seen a thermo bent, as yours are. When you replace it you might consider replacing your block as well. I'm not a kiln expert but maintaining straightness might not be a bad thing?