Annealing Ornaments and bending

[ginkgoglass]

Just got done with half of a custom ornament commission yesterday and when I opened the kiln this morning, they are bent.

They are all blown long icicles which I annealed at 1018 F because my kiln is too high by 32 degrees. (Thats what I set the temp at on the controller) They did soak in there at that temperature for 6 hours after I finished working so I'm wondering if that was the problem. I also noticed that a red vase turned orange and opaque in the same kiln but I had two other red ones in another kiln and they stayed transparent red.

I am so upset! What do you anneal your blown ornaments at?
I don't know what to do. I guess I need to start over.

Edited to add: ARGH!!

[LarryC]

Lana, I anneal everything at 1050 but I do garage at 950 prior to ramping up. This is based on recommendations received in conversation with some of the color manufacturers. All kilns will vary a bit as you know so these numbers may not be good in your setup. Slumping at 1018 is a bit surprising though.

[gmkcpa]

Boro? There's no way boro would soften up enough at 1150 to bend, let alone at 1050! If I was a betting man I'd bet that your kiln temperature was whacko and not what your thermometer or other temperature measuring device says.

To answer your question: I anneal everything at 1050. With certain pendants I'll heat them up to 1150 for 20 minutes, then let them sit at 1050 to anneal. NEVER had your problem.

[menty666]

I've actually seen thinner rods bend slightly at the lower (normal) temperatures. I had that happen with some stir rods in the 10 mm range.

[ABR Dave]

Are they purely clear? That can make a difference I've found. However, I would lean to a controller/ramping issue with the kiln. What type of kiln and controller?

[ginkgoglass]

I anneal everything at 1050 normally.
I just noticed that boro things were bending such as stems on flowers (7 mm solid rods)and soft glass (which I rarely do) was sticking to the fiber blanket etc.
The pieces were clear boro icicles and really not that thin walled.

I think the kiln is way off whack too -- just wanted to check before I contacted the maker. Maybe I've got a bad thermocouple. Do I need to get a pyrometer? I thought that's what the kiln controller does.

[LarryC]

Check that the thermocouple has not backed out of the kiln cavity. That might cause overtemp. A pyrometer is not necessary but it is nice as a second source to check the kiln temps.

[fyrsmith]

You need a calibrated pyrometer, so you can check the temp in various locations in the kiln. One interesting test is to get a stick of something like double amber purple that came from the maker transparent. Put it in the kiln with one end against the back wall and the other sticking out the front (bead door?). I bet you will see a color variation from back to front, indicating a difference in temp front to back.

[patienthand]

for delicate things I anneal at 1025 for a longer period. Back in the day i did a lot of thin goblets and blown work, and this worked for me, and I didnt have sagging issues.

I suggest you take a 3mm rod and set it an angle in your kiln and gradually bump up temps till it sags,, then you know roughly what temp to set your kiln at for delicate stuff. And your kiln will not be the same temp at the top, back, front or sides... find your sweet spots

[PittsGlass]

These are all good methods of double checking what your kiln is doing. The thermocouple could be too low in the chamber causing the excessive temperatures. There is something to be said about long periods at annealing temp, but slumping should not be one of them.

A pyrometer will give you a good idea of what is really going on in the chamber.