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Mug

Cone 6 Casting Slip

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OK... not sure where to start.

I have purchased a blunger to mix 30 gallons of slip and hopefully mix a 55 gallon drum with it in the future. Mainly the goal was to be able to reclaim efficiently. I was also hoping to reduce the material cost of the casting slip. From what I have read some people imply the savings could be 1/2 the cost of pre mixed casting slip.

 

Currently standard ceramics cone 6 stoneware casting slip is reasonable and if it is purchased in quantity the price is hard to beat. As an example: On a 275 gallon tote it's about 50.00 more to buy it ready to use. The problem with Standards cone 6 is that you really have no idea whats in it and you have little control of it's characteristics. Their cone 6 has worked well for me so far, but It could be a little better for the detailed molds I'm using. I also have used and like both types of their porcelain. These are all around 13-14% shrink and less than 2% absorption. The shrink rate is important to me, it's very close to other clays that I use. I'm surprised the shrink rate is not ball parked in many of the slip recipes that I have seen.

 

I have a couple of recipes to try in the mid fire range.

cone 7 slip Hensley/ Polseno from Andrew Martin's book....costs about the same as the pre mixed

Cone 6 Andrew Martin's white porcelain... This would be about half the cost of the pre made porcelain.

 

Would these recipes be a good starting point?

Some of the ingredients like frits are pricy. I'm sure other people cringe at the thought of buying a bunch of raw materials that may end up sitting on a shelf. Are there some must have starting point ingredients?

Are there any recipes for a cone six stoneware that would come in a 50% savings?

 

 

 

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Thanks Neil

Standard is hard to beat for ready made material. After having a business with a larger profit margin I've been trying to make adjustments without cutting corners. I have to keep every penny for pottery!

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The mixer works great for reclaiming as expected, that was the main goal.

 

It seems feasible to come in at half the cost with raw materials, but you would have to use a different materials.

I'm not overly concerned about the mixing issues, I have a fresh air mask and out building that could be dedicated to Glazes and clay slip mixing, this should minimize exposure. The mixer should be able to run by itself until the slip is mixed. I feel it would be worth the effort to mix your own if the materials could come in at 50%. 

 

I found a slip recipe that uses cheaper Nepheline Syenite instead of Feldspar. Oddly enough it has no ball clay. I'm not remotely sure what is a good or bad cone 6 slip recipe.

Grolleg                    63

Nepheline Syenite   25

Silica                       12

Most people seem to use Nepheline Syenite, Andrew martin used a little of both.

Is there a reason that you would not want to use straight Nepheline Syenite?

 

 I see that many of the recipes use the more expensive Grolleg over the domestic Florida, Tile 6, or Georgia Kaolin. Is their any reason why you wouldn't use it, besides the slight color, Iron and Titanium content? I would also like to promote the idea that the clays are domestic instead of an import if it makes sense.

 

This may sound out there, but we have a Kaolin mine that's like 4 miles close, anyone every use kaolin from North Eastern Ohio? Is it even any good? I haven't seen it listed for sale from clay suppliers, from what I understand it's mined from under the coal beds and it is smooth almost pure white kaolin. I know a guy who works at the mine who can set aside a couple of tons of the cleanest clay at a low cost, if I wanted to mess with it.

 

Slip storage: If you mix 20 to 30 gallons of slip, would you break it down to smaller containers or set a time clock on the mixer to keep the slip agitated?

 

I apologize if I ask to many questions at one time, with ceramics there are so many things to grasp, I just want things to make financial sense, before investing aimlessly.

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When I had a slip casting business on the side (side of a full time throwing business) I found a cone 10 slip that worked and I bought it by the ton. Clay is cheap- to keep it from warping I added another 5% EPK-but that was the only dry material added. I think you will fine that buying dry slip in bulk is way easier and time wise is a no brainer over all the materials you need to mix a batch. One ton in 50# dry bags is really the only way to go.You only you know whats your time worth.

We mixed in a 55 gallon blunger-home made with a commercial slip mixer and pump system.

I have no help as to a cone 6 recipe.Sometimes low cost costs more than high cost in the long run.

Mark

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I found a slip recipe that uses cheaper Nepheline Syenite instead of Feldspar. Oddly enough it has no ball clay. I'm not remotely sure what is a good or bad cone 6 slip recipe.

Grolleg                    63

Nepheline Syenite   25

Silica                       12

Most people seem to use Nepheline Syenite, Andrew martin used a little of both.

Is there a reason that you would not want to use straight Nepheline Syenite?

 

 

 

I think this recipe may be a it loose at cone 6. I would do a small test and check the absorption rate. There's no ball clay in order to keep it white. That's also why it's using grolleg instead of domestic kaolin. Personally, I like some ball clay in casting slips because it gives the pieces considerably more dry strength. But as long as there's ball clay in it there's no sense spending money grolleg. Ultimately you'll have to test a bunch of recipes to see what you like. Keep googling and you'll find more recipes.

 

As Mark said, the cheaper materials price does not alway equal more profits. Labor is the number one expense for potters, so the more time you can spend making work instead of making slip, the better off you'll be. Plus if you're not familiar with clay body formulation and such, you're going to spend a lot of time testing and/or making mistakes when you could be producing. 

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Hi Mark

The 50# bags would be easier to transport and store. It's interesting that adding EPK at 5% made a characteristic change. I want to get to the point of casting at least 50 gallons at a time. My goal is to have my son handle the casting and mold making. I get the impression that you don't really slip cast any more. What made you decide to get out of that end of the business? 

 

Hi Neil

Thank you for your input on the recipe, I understand the purpose of the Grolleg a little better and why you might not want to mix it with ball clay.

Sturdy green ware is a plus, It's a real time sucker when it is more fragile than an eggshell.

Lord knows I'm a sculptor and not a chemist, asking a few questions helps narrow down whether it's worth pursuing.

I like slip casting, because once the sculpture and the mold are made, it is repeatable by the average person. If you have enough unique designs you should never be out of work. I would like to focus more on the wheel, but it's tougher finding someone who can throw. If my focus is on slip casting, design and decoration, I hope by learning more it will be time well spent

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Mug

I went into a partnership with another potter in 1993 to slip cast cone 10 reduction fired aroma therapy lamps. We where approched to make many thousands by a larger company that sell herbs nation wide. Both of us potters had our own funtional pottery business. We ran this on the side. I personally cannot stand working on the same form over and over as you do in slipwork. We shipped many pallets of these lamps across country when the buyer moved East. We double boxed them all into the sales box they sold in stores in.

My life is wheel based throwing different forms not makeing the same darn thing 20,000 times until I go crazy. I digress as the business really only needed one to manage I bought out my partner and moved the operation.

I located it away from my shop. after about 10 years the intire demand slacked and I stopped when the orders slowed and never went looking for more slip business. The reason to add the EPK was to get a cheap source of alumina so the body did not slump at cone 10 as the form had a huge hole in the wall for the candle to fit and EPK is cheap.The body was a commercial mix that was porcelain abd the small amount of EPK still kept it white.

The slip was from Laguna clay co called MC porcelain and even though those are my intials its not named after me.We used many a ton of this material.

And as you guessed I am out of the slip business.

When learning ceramics one needs to learn all the processes and slip is a just another process one needs to learn. For me its a mass produced form tecnique and thats really not what I'm in to.All the shows I do do not allow slip wares in the jury process.

Mark

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That makes sense, I understand how you feel, repetition is mind-numbing torture. My idea of casting is to get out of the actual casting process as soon as possible. I currently need to make things that are repeatable by anyone.

My middle son was in a car accident, a really bad accident that left him in the hospital for 6 months. He has recovered to some extent, but the head trauma he sustained has left him changed. He was a true multitasker and now he gets anxiety when he has several things going on at one time. Now I'm not sure if he will recover 100%, but he is still making progress all be it slower. I figure if I can create new sculptures and get him set up in casting and mold making it will be a win win. As the slip casting expands, my intent is to hire someone to handle casting, glazing firing ware. I'm trying to do the things few people know how to do, creating new ideas and then making a pattern or sculpting things that will be molded. The problem with making new production molds is that there is a lot of trial and error before you reach a sound prototype.

 

I have been trying to achieve a well rounded education in ceramics.  I've been working on ceramics for about 4 years now and have lots more to learn.

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Mug-

 

I'm very sorry that happened to your son and hope he recovers 100%. It just broke my heart to read that. I only have one child, a son who is 16. He had to have minor surgery while we were on vacation in Africa. I was freaking out! I think it is great that you are exploring this to get him involved too.

 

Best of Luck,

 

Spring

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