slumping into a candle holder

[ajda]

Good advice from Chas - if  you want a result that you are happy with and confident you can repeat in future, be prepared to sacrifice the odd piece in the course of experimenting. Some glass doesn't like being re-fired too many times - it may start devitrifying, for example - but I think most Bullseye should be good for multiple slump firings. I've been playing with their Opaline Striker - the more you cook that, the more milky and opaque it becomes, a change which is non-reversible - I've messed up quite a few nice pieces trying to get it just right. Even if you seriously overcook a piece and end up with nothing but a warped puddle you'll have learned something in the process! Another bit of good advice would be to keep detailed notes on every firing...

[sandmor1]

Hi Chas, thanks for the advice.

I slumped the piece again, going up another 20degs and once again it was slightly improved but not what I was hoping for.

The candle holder part of the dish has straight sides about 3/8" deep with a 3" diameter base but the piece just curves down to a flat bottom about 1" across without touching the straight sides. Maybe I have got this wrong...should it follow the exact shape of the mould or just a droop?

Actually it is quite nice as it is and I am going to give it to my daughter in law for her birthday next week but I am going to try another one maybe going up another 10/20 degs. But if I still just get the same droop rather an definate drop on the sides then I can live with that.

Sandra

[chas]

Sandra, at the point where the top drops into the holder, is the transition 'over the edge' sharp or rounded?

There is no reason I can think of why you shouldn't get a better representation of the mould shape - other than the experience I had with a similar mould.

In my case it was made from Kaiserlee board and as well as increasing top temperature and hold I was able to round the edges to promote an easier slump. Most likely you won't want to modify the mould at first - but do try upping the top temp again and experiment with a piece of new glass. You may need to be well into the 750+. The other, slim possibility is that in slumping it is trapping air. If the mould is well designed and proven, it shouldn't be a problem - but  there's often air holes: have you blocked them with kilnwash?

To give you some idea of the variables that may apply, here's some info from our experience:

Warmglass basic schedule for Bullseye: 4 hours up to 673deg hold for 10 mins

Our general approach for float: add 15 - 20deg

Our final schedule to get a flat bottomed drop  in the project mentioned: 4 hours up to 835deg hold for 35 mins.

As said before, nothing intuitive, all from experimentation and note taking, all kilns are different, but see how different it can be in the same kiln but with different moulds.

Good luck,

Chas

[sandmor1]

Sandra, at the point where the top drops into the holder, is the transition 'over the edge' sharp or rounded?

There is no reason I can think of why you shouldn't get a better representation of the mould shape - other than the experience I had with a similar mould.

Our general approach for float: add 15 - 20deg

Our final schedule to get a flat bottomed drop  in the project mentioned: 4 hours up to 835deg hold for 35 mins.

As said before, nothing intuitive, all from experimentation and note taking, all kilns are different, but see how different it can be in the same kiln but with different moulds.

Good luck,

Chas

Chas, it is rounded, definately not sharp which is what I had in mind.

I will try again in a few days when I have finished firing the other pieces I have ready for the kiln. ...

I do love this hobby but my little Hotstart is just not big enough...I will have to increase my "donations" to the lottery 

Sandra

[Moira HFG]

Sorry if this is obvious.....have you checked the air holes in the bottom of the mould aren't blocked with batt wash? If the air in the bottom of the mould can't escape, it might stop the glass from slumping into place properly.

[sandmor1]

Sorry if this is obvious.....have you checked the air holes in the bottom of the mould aren't blocked with batt wash? If the air in the bottom of the mould can't escape, it might stop the glass from slumping into place properly.

Thanks Moira, but No, the holes are clear as a bell....

[Warm Glass UK]

Please pick up the phone and call our Technical staff for advice on this if you need to (01934 863344) - we offer free technical advice and support on any kiln that we sell for as long as you need it (and some need it for a long time I can assure you which is totally fine by us). It's really important to us that if a customer has invested (alot of money) in a kiln, then they get to be comfortable with it and understand how to get the results they want. The best people to speak to are either Simon or Megan for Technical advice.

[sandmor1]

Please pick up the phone and call our Technical staff for advice on this if you need to (01934 863344) - we offer free technical advice and support on any kiln that we sell for as long as you need it (and some need it for a long time I can assure you which is totally fine by us). It's really important to us that if a customer has invested (alot of money) in a kiln, then they get to be comfortable with it and understand how to get the results they want. The best people to speak to are either Simon or Megan for Technical advice.

That is kind of you, Thank you.

I am going to have another go next week but if that fails to achieve what I am looking for I will call.

Sandra