Blue No Blue

Glaze testing. Recipes for glazes are everywhere. Just goggle. Or buy a great book like John Britt's "The complete guide to High-Fired Glazes" and you find pretty pictures and the listing of materials that if combined and applied will lead to beautiful pots. And they often do. But, somewhere there is fine print which basically says: "Your results may vary..." There are multitudes of reasons for this. The materials differ from mine to mine or even different locations in the same mine. Your application isn't the same. You don't follow the exact same firing schedule. Etc. Etc. So you do tests. As I am in search of my "style" and body of "coherent work", I try to put glaze tests into the kiln when I fire.

Recently I had the opportunity to do back to back firings in my gas fired Soda Kiln and then in my friend, Rob Harvey's, wood fired Salt Kiln. So I made duplicate test tiles for each kiln. The clay used was a stoneware made by Highwater Clay of Ashville, NC called Orangestone. The results were interesting and are shown below.





















Okay, so? Well, they are different from kiln to kiln. Surprise? No. They are different from Soda to Salt glazing. Surprise? No. They are different from gas to wood fired. Surprise? Again, no. The tests also failed to find a nice blue. Lots of green, but blue? No.

So was it worth doing? You bet. I got two glazes that are working in both kilns right out of the box, Emily's Purple and Gold Shino. Plus a couple more that may work with a little more... glaze testing.

The pressure is on!

Middle Tennessee Gas Company came out in the rain and put pressure gauges into the system at several places. One before the regulator, one after the regulator before the meter, one right after the meter and another where the line change to 1/2 inch piping. Now with the two gages I have at the burners, that makes 6 gages in total. What fun for an engineer!

Took just a minute of running the system to determine that the orifice in the regulator was too small. It took just another minute for them to replace it. The pressure at the burners is where it was designed for.

Now, it is time to make some ware and see if it will reach temperature. [It also has to get warm enough so all my clay isn't frozen solid]

Close, but no cigar

The gas company's contractor and installed the new flow suppression device. I was banging away on my computer when I heard the backhoe.



The device is really nothing more than a spring and a ball. In the small one that was in there, you can blow into the end and make it close.



The scale of the photos distorts the difference in size. The new one is about 4 times as large. You can blow yourself blue; you won't get this one to close.



I was curious about how they connect the pipe. It is welded using "irons" that they heat to about 450 degrees.



They have mechanical guides the bring the pipe together once they apply the heat to it. Makes sense, just never seen it done before.



The whole process of changing out the device took less than an hour.

After they had the new device installed, I fired up the burners for another test. No shut down, but it still is not developing they pressure I want. My guess is that we have the kiln piping undersized and are not getting the flow needed. The gas company is coming out next week with pressure gages and we are going to troubleshoot the system. I think I will run some numbers and give Ward Burners a call.

That's why you do tests

Been off on a trip to Florida to help my daughter move and attend a family Thanksgiving reunion. It was fun, but now its back to kilns and pots. I was inspired by a stop to the Clay & Paper gallery in Dunedin, FL. I got to see a number of potter's work including McKenzie Smith's. I took a workshop of his acouple of years ago and I really enjoy both him and his ware.

The test went well up to the point where I tried turned the burners up to full operating pressure. I turned up one burner and was only able to get 5 psi. I tried to turn the other up and the pressure on the whole system dropped to less than 0.5 psi. I shut the system in and went away for about 30 minutes and then tried relighting pilots and burners. They worked as before the drop. I slowly turned both burners up and when I got to 4.0 psi on both burners, it shut in again. Had to be a safety device on the line. I checked with the engineer at the gas company and he said it could be the regulator or a federally mandated flow suppression device that was under sized. They are due here in a little while to dig up the line at the connection to the town supply main to replace the flow suppression device with a larger one. Then they want to run the burners at maximum pressure to verify that was it. I am warming the kiln just because I am a little nervous about throwing that much heat at a cold kiln.

Hopefully, this will get me my 6 psi design operating pressure.

Kiln done, commisioning underway!

I lit the remora burners (pilots) this morning and the kiln is drying out. I am holding it at about 225 degrees for a few hours. Then I am going to ease it up to red heat to get a feel for it. Then, I really need to start making pots.

One of the last tasks was to put a "wash" on the hard brick to help them withstand the effects of the soda/salt. The product I am using was recommended by Larkin Refractory Solutions. It is a high alumina refractory plastic (Econoram 90 TR by Pryor Giggey Co.)



I also added the IFB floor to the firebox and floor flue. The IFB was dipped in the Econoram wash before placing. Hopefully, these will help protect the hard brick in these high heat, corrosive areas. I had a couple of Super Duty hard bricks to use as target bricks.



I cut 9" sections of a kiln shelf to use as the interior flue roof. When I am using soda/salt I will use coils of wadding to keep these from glazing to the floor.



This is how the shelves layout. As you can see the hot gases are forced to the center under the set to leave the kiln. Hopefully, this will give uniformity in heat top to bottom, front to back.



When I start up this morning, I used a weed burner through the passive damper hole to heat the chimney and start the draw. I don't think this is going to be necessary except in really cold weather and maybe not even then.

Well , the first step in making pots is cleaning up the studio. It has really gotten trashed the last couple of weeks.