annealing / striking for northstar 88 (pomegranate)

[dbvanhorn]

I am looking for info on the proper temperatures for annealing the pomegranate so as to get the color to strike.
I know there's a doc but I can't access it on the northstar site.

I have my new glass bench operational, and last night was the first session with my torch, oxycons, etc. I made a little marble with cobalt and pomegranate, and after a run in my new kiln (Chili pepper, program 4) the blue is there but the red is not.

[Mr.P0rn]

My cycle is garage at 1070, anneal at 1060 for 2 hours, drop 2.5-3 degrees per minute. With this, I get a nice deep red, but it's not so dense that it can't be layered over an opaque sparkle. It's never given me any trouble or failed to strike. Try it out, and if it isn't dark/opaque enough, strike at 1050ish for 30 minutes until desired effect.

[dplaza]

my kiln has cool spots or something because if i want everything in it with pomegranate to strike i need to soak at 1100. 1050 works on anything near the coils. its a good color to use to get an idea for the temperature gradient in your kiln for this reason. now i just run at 1100 any time im doing something im worried about cracking.

i once allowed it to ramp up well over 1200 by accident and i opened the whole door and watched the color turn from pink to deep red as it cooled, that was rad to watch but i did slump a few dabbers.

[dbvanhorn]

I won't have that problem, my kiln is the AF3P "Chili Pepper" and it won't go over 1100.

Ok, I will have to get out the manual and see if I can write a program for the kiln for striking. Should be fun. Thanks for the advice!

One question: Why would you garage at a temperature higher than the annealing temperature?

[Mr.P0rn]

^^^This is an awesome, awesome question.

Basically, the longer you hold the kiln striking colors like pomegranite, the more they strike. If you use a higher temp, it strikes faster. This is an important relationship, and helps you really control exactly what you strike to. You can strike at a lower temp to expose more of the gradient of the strike, or strike hot to just make a dense version of the color you're using. Milon Townsend's book "Advanced Flameworking" has a cool little table of pictures relating to this.

As far as why i personally garage at 1070+....let's talk about chromium based greens and sparkles. They usually check because of extended garage and annealing times. At a certain temperature, the chromium grows crystals in the glass matrix, and when the growth exceeds that which the glass can handle, it checks because the crystal growth is physically shearing the glass molecules apart. Like striking colors, if you hold it for a long time, the crystals continue to grow, and as you increase that temperature, they grow faster. Once you go over a certain temperature, it's hot enough that crystal formation isn't favored, and chromium won't give you trouble because the crystals aren't forming. Doing this to the glass first also seems to make it tolerate my kiln schedule, I've yet to ever check anything. Once i realized this worked pretty well, i started deep encasing balls of unobtanium in opaline to use for bails, then took them out and worked them into bails until they were cold, and then annealed for over 100 hours at 1050 to see what would happen....nothing.

I initially started doing this because of fuming though. My thought process was that striking happens around 800-900, and if you open the door to the kiln, and a fume piece is right by the door, it could drop enough to slightly strike, and this happening over an entire day could be significant. So, I run my kiln hot because it holds the glass well above the striking temperature, and ensures that i don't get any kiln striking. My kiln schedule never seems to change my fume color, it just comes out -slightly- more brilliant, but almost always the same color. As a general rule of thumb, I don't flame or kiln strike (unless it's one specific type of purple comb), so a lot of my focus with my fume is keeping the colors from changing once i get them right.