rim and slump questions

Sandpiper · Post by **Sandpiper** » Sat Jun 07, 2003 9:03 am

I just finished a bowl that turned out pretty ok

But, it's has two small problems. The first problem is with the rim. I cut it out Patty Gray style. Wow, that worked great

. I cut an 11 inch circle in clear for the base, then I cut a rim with an outside diameter of 11 1/4 and an inside diameter of 9 1/2. This was also in clear. I filled the remaining center. When I fused the piece, the seam healed nicely, but where the 1/8 overlap was there is a small u shape missing. Like the seam opened where it rounded over the bottom base. How do I avoid this in the future?

Second question. I slumped this blank into a mold that is 11 inches in diameter and 2 inches deep. The bowl came out 9 1/4 inches in diameter. I assume I slumped too long and the glass started to pool in the bottom. Am I right? I think in my concern to be sure in has slumped all the way to form the bottom, I'm going too far.

Oh yeah, I used Spectrum 96 glass and the over all thickness was 1/4 inch. I followed the recommended schedule from Spectrum for the fuse and the slump for this thickness of glass.

Thanks ahead of time for any help you all give,
Sandpiper, alias Robin

Marty · Post by **Marty** » Sat Jun 07, 2003 10:09 am

Robin- for the first, cut both the rim and the base to the same diameter.
Re the slump, you will lose diameter as the glass sags into the mold. Is the glass thicker at the bottom? If yes, then you probably slumped too high and/or too long. What temps and how long? Marty

Sandpiper · Post by **Sandpiper** » Mon Jun 09, 2003 9:54 am

Thanks so much, Marty,
You confirmed my suspicions. I thought about cutting the rim the same size, but I wanted a nice rounded edge. I will know better next time.

I also knew it would shrink some, but I never expected that much!!! The bottom seems a tad heavier, but overall the glass is thicker everywhere. I did notice the iridized coating looks a little wrinkled so I'm guessing it did start to pool toward the bottom. I fired the following sched.

400dph to 1000, 1200dph to 1225, soak 15 min, flash to 1100, hold 8 min at 1000, 300dph to 955 hold 20 min, 200dph to 800, 400dph to 150.

I seem to have noticed that my kiln is accomplishing things at a lower temp than the literature suggest. Perhaps my kiln is reading the temp wrong. Should I get those ceramic cones and run some sort of test, or just start paying attention a whole lot sooner.

Thanks again for helping out this newbie,
Sandpiper, alias Robin

PaulS · Post by **PaulS** » Mon Jun 09, 2003 10:17 am

Sandpiper wrote:I seem to have noticed that my kiln is accomplishing things at a lower temp than the literature suggest. Perhaps my kiln is reading the temp wrong. Should I get those ceramic cones and run some sort of test, or just start paying attention a whole lot sooner.

This is a good test Robin;

http://www.bullseyeconnection.com/pdfs/ ... tes_01.pdf

Paul

Sandpiper · Post by **Sandpiper** » Mon Jun 09, 2003 11:51 am

Paul,
Wow, great info. Thanks so much. I guess I have some work to do!!!
Sandpiper, alias Robin

PaulS · Post by **PaulS** » Tue Jun 10, 2003 5:35 am

No problemo, the BE site has some great resources.

Post here if you need more help okay.

Paul