reporting back re: itty bitty drop molds

[Carla]

I have tried two different metals, thin sterling silver and heavier gauge brass as my small drop rings. I coated both with BE kilnwash. The metal drop plate/rings were apx 1.75" x 1.5". The tear shaped drop hole 1" x .75". I cut the glass to be slightly smaller then the plate size.

I tried 3 different approaches, all w/ BE thin clear as I hoped it would be a very "movable" droppable glass:

1300° w/ a 1hr 30 min soak:
I got some dropping, enough for my purposes. The silver "tarnished" the glass thru the kiln wash, the brass did not. This surprised me as brass is considered a dirtier metal.

1325° w/ a 1hr 30 min soak:
No significant increase in the drop, but the flat edges deformed quite a bit by sucking in towards the drop. Decided that I was too hot and the glass too liquid so I returned to the lower temp and a longer soak.

1300° w/ 3 hr soak:
No significant increase in the drop! What a surprise, for me. Even after all that time in the kiln. Also I literally dropped one of the samples and broke it. But that offered the opportunity to see if the glass significally thins as it drops. Not really.

Maybe this is what you all were trying to tell me. That in shapes as small as I was going for the mass of glass just isn't enough to drop. But I was really hoping for a very dramatic drop. Rats.

So I will puzzle on this for a while and see what I will do next. Any advice will be gladly accepted.

Carla

[Jerry Barnett]

Congratulations on trying.

In case you don't know, silver will stain glass that is in direct contact with it. You may be seeing some of that effect even through the kiln wash. Of course, the good news is that brass is cheaper.

When I do multiple layer, much larger opening drops my rule of thumb is a glass blank that is at least 2" larger than the opening all the way around. I can't give you any guidance for a single layer drop of the size you want, but increasing the amount of glass sitting on the drop mold will reduce the degree to which the sides suck in.

A tear shaped drop will be more resistant to movement than the same area circular shape because of the pointed area of the shape.

Another experiment you could try is to go to 1300 and hold there until you have 1/2 to 2/3 of the depth you want; go to, say, 1385 long enough to get your desired depth; and then crash cool your kiln to 1100 to stop the glass movement. Potential Cautions: You will need to watch the drop closely; need more glass outside the drop opening to keep the sides in place; run a greater risk that the metal mold will trap the glass; and have thinner side walls as the glass descends further. And, of course, it may not work.

Jerry

[Geri Comstock]

Hi Carla -

More layers of glass, or thicker glass may help with it dropping further. More layers of glass implies that you need to fuse it first. Thicker glass means that maybe a thicker float glass would work.

Geri

[charlie]

Maybe this is what you all were trying to tell me. That in shapes as small as I was going for the mass of glass just isn't enough to drop. But I was really hoping for a very dramatic drop. Rats.

if you want a dramatic drop, you need to really increase the temp a lot. however, that makes the walls be very thin. you then have to use a thicker blank to solve that problem.

[Carla]

In reply to those of you who suggest more glass...as in thicker....can I instead go with a bigger blank?

I am not interested in the flat sides around the drop. Those will be cut off. All I want is the hollow bubble made by the drop. This is what I will set as one would set a cabachon.

So, I'm thinking a bigger piece of glass might make for a larger drop, with more edge distortion but cuz I don't care about that, it won't matter.

Sound logical?

Also I think I may have a way to get around the silver stain. It's interesting because the thing that makes sterling silver tarnish is the copper in it. Brass has lots more copper. Fine silver (or 100%) silver is what enamel people fuse to when making their pieces, copper being the other metal.

Carla back to her kiln, with new ideas.

PS: Do you all want me to keep updating you or should I just go my merry way? Please email me privately: foxon@bendnet.com
I don't want to burden this forum with useless mutterings if people don't want to read them.

[charlie]

what do you mean by 'bigger'?

it's the span/weight ratio that causes a drop. the larger the span, the less weight you need (thinner) for a drop at a certain temp.

if you increase the temp, you can decrease the weight or the span, or both (but not as much for each individually).

if you decrease the temp, you have to increase the weight or the span, or both, down to a certain point, at which point you won't get any (or extremely slow) slumping.

keep reporting back. i'm sure someone will be along in the future to ask the same question. after all, nothing's new (to quote another, long running topic).

[Carla]

what do you mean by 'bigger'?

it's the span/weight ratio that causes a drop. the larger the span, the less weight you need (thinner) for a drop at a certain temp.

if you increase the temp, you can decrease the weight or the span, or both (but not as much for each individually).

if you decrease the temp, you have to increase the weight or the span, or both, down to a certain point, at which point you won't get any (or extremely slow) slumping.

keep reporting back. i'm sure someone will be along in the future to ask the same question. after all, nothing's new (to quote another, long running topic).

I mean using a bigger span as you put it. Make the plate bigger, hole the same size and see if a bigger piece of glass will drop farther.


When I went up in temp (25°) I did not get a significant increase in drop, just more edge distortion. But I am doing a very small diameter drop so significant may be hard to see.

I'm going to keep at it. I never like to be stumped.

Thanks for your thoughts.

Carla

[charlie]

I mean using a bigger span as you put it. Make the plate bigger, hole the same size and see if a bigger piece of glass will drop farther.


When I went up in temp (25°) I did not get a significant increase in drop, just more edge distortion. But I am doing a very small diameter drop so significant may be hard to see.

I'm going to keep at it. I never like to be stumped.

Thanks for your thoughts.

Carla

then no. span refers to the diameter of the hole. the part supported by the flat plate has no affect on the depth of drop.

you may have to go up 50-100F for small spans. i once tried to get a 4" square 1/4" thick blank to slump over a 3" square tile (looking for 1/2" legs on the tile). it took a LONG time and a much higher than normal slumping temp.