Comment

Comment by Maulik Oza on June 22, 2013 at 7:20am

i know.. it is very good experience in working with this kind of kiln and factory. this is tunnel kiln about 60 to 70 feet long, in which all these trollies goes one by one from one end and come out from another end.  but the firing cycle is pretty fast.. cooling to cooling it takes only 14 to 15 hours..

And yes i have seen robert compton's car kiln.. it is superb. i am a big fan of him.. i have also tried for internship in his studio but now i think he doesn't take students. but i wish to visit his studio once .

regards,

oza

Comment by Norm Stuart on June 21, 2013 at 9:29pm

Pretty nice to have access to a factory like that.  Is the trolley kiln continuous or does the kiln fire one car at a time?

For people who've never seen one, this website has photos of a single-car trolley kiln in Vermont, where the trolley is both the kiln floor and the door.

http://robertcomptonpottery.com/Kilns-Compton-Gas-Fired-Kilns.htm

Comment by Maulik Oza on June 21, 2013 at 9:06pm

have a look,

regards,

oza

Comment by Maulik Oza on June 21, 2013 at 9:00pm

hi,norm..

thank you for your in depth reply as always.. you are too good.

first of all i didn't know that if i asked in status update no one can reply. so next time i will start a discussion so many other can join in. :)

other thing about cone 2 glazes.. you are right here also many commercial stoneware makers use cone 2 glazes to save on firing cost. why i want this cone 2 glaze because i want to get one of our product mass produced  in factory. The glaze they are using is not really appealing to me. so i wanted a different glaze for the same temperature.

body is not a problem because we are using their slip for slip casting which gets matured at this temperature. right now for glaze they are using commercially available transparent frit and china clay in proportion of 90:10. so i will try to modify this glaze itself by adding some new materials to it as you said.

i am attaching some photos just for your information..have a look. and i will give you another update as i go further.

regards,

oza

Comment by Norm Stuart on June 21, 2013 at 11:00am

Firing to Cone 2 -- 1,142 C is quite uncommon in art ceramics, but Paul Linhares fires his work to Cone 2, after "bisquing" to Cone 010.

http://www.mudskipperpottery.com/process.html

Linhares has a background in commercial stoneware production, with each artist making thousands of pots each year, so I suspect many commercial stoneware makers also use Cone 2 to save money on firing costs.

You asked this in an "status update" which no one can reply to, so I'm attaching this answer to one of your photos.

The problem with a Cone 2 glaze is that this is just below the temperature where most feldspars melt, which are the most common fluxes in Cone 6 glazes because they're less costly. This means you need to add more low-temperature flux, like man-made frits which typically melt from Cone 018 up to Cone 08. Or you can use high-boron materials like Gerstley Borate.

http://digitalfire.com/4sight/material/frits.html

To make a Cone 2 glaze I would start with a Cone 5/6 recipe and add about 15% man-made frit to the recipe.  I'd increase or decrease that percentage until I achieve the correct fluidity at Cone 2. This means Cone 2 glazes will be more costly than Cone 5/6 glazes, but you'll save on firing costs.

If you look at Paul Linhares "High Alkaline Clear" glaze on his website, it relies on 40% man-made frit with the addition of 15% Gerstley Borate which melts at the same temperature for a total of 55% frit equivalent.

Low-fire glazes (Cone 06 to Cone 04) typically have 80% man-made frit.  Typical Cone 5/6 glazes relying on frit are typically 40% man-made-frit.  So it's easy to see why Linhares ends up using 55% frit one his Cone 2 clear. Glaze with refractory colors will require more than 55% frit.

The other problem you'll face at Cone 2 is prepared Cone 5/6 clays will not densify fully at Cone 2 and will break easily.  The solution would be adding a "body frit" (something like Ferro Frit 3110) to the clay so it fully densifies at Cone 2. This is actually the most common method manufacturers like Laguna Clay use to make a Cone 5/6 clay body. They start with Cone 10 clay and blend in Ferro Frit 3110.

Good luck with Cone 2.