Problem slumping small dish

[Trudi]

Hi

I've just tried slumping a 6mm thick piece of glass into a new mould – it's a dish mould 9x9x3.5cm
http://www.warm-glass.co.uk/extra-small-square-slumper-with-flat-base-9-x-9-x-35cm-p-2979.html

I followed the basic slump schedule on warm glass but it has barely started to slump at all
– BASIC SLUMP
Runtime = 12 hrs
RATE TEMP HOLD
Segment 1 167°C ( 300°F ) → 663°C (1225°F ) 10 min
Segment 2 999°C ( AFAP°F ) → 482°C ( 900°F ) 60 min
Segment 3 56°C ( 100°F ) → 371°C ( 700°F ) End

Would I be better off using Elaine's schedule posted up for slumping bottles ...
Seg. Rate Temp Hold
1 278 593 10
2 139 704 0
3 Full 804 5
4 Full 554 60
5 56 399 0

Thanks x

[qwirkyglass]

hi trudi,

Im sure someone with more knowledge than me will follow me on here, but i will try and help.

What glass are you using? if its bullseye then they have good slumping schedules online somewhere in their technotes.
If it were me i would try changing one variable but keeping the others the same on your original cycle, maybe take the top temp up 20degrees and try that first, if you piece started to slump then you are close.
i would be worried about using a bottle slumping cycle for non bottle glass as you may end up with a puddly mess.
the other thing that may affect it is if you have blocked up your air holes at the bottom of the mold with your battwash or thinfire, as this can cause you to trap a bubble which will stop slumping.

Hope this makes sense

[Zeldazog]

Trudi, if you look on the same page as the mould is on, there is general mould instructions to download - you should find your answer on there. 

[Trudi]

Ah ha .... thank you for that ..... will have another go x

[SueP]

My note book and schedules are at the unit but I had this on my pc so this would be what I started with before I tweaked them to suit my kiln.

SLUMP with BULLSEYE (6mm)

1. Initial Heat (Process Soak)   155/hr to 704C   0.20

2. Rapid Cool    AFAP or 9999C/hr to 516C   1.30

3. Anneal Cool   26C/hr to 371C   0.00

5. Cool to room temp.   AFAP or 9999C/hr to 25C   0.00

You certainly don't need to go as high as you do for bottles so why not try the above.  I have the same mould and have stumped successfully into it in one go so the above schedule won't be far out

Suex

[MeadMoon]

Here's my slumping schedule for 6mm thick Bullseye glass into a mould deeper than 1cm:

Seg   Rate   Temp   Hold
  1      200     520       25
  2      300     680       10
  3     Full      482       60
  4       60      370         0

I tweak Temp 2 and Rate 2 according to the thickness of glass and depth of mould, but 680 is the temp that I usually use, although I've also used 690 on a couple of occasions.  Hold 2 can be from about 5 to 20 minutes.  Sometimes I watch the slump and skip to the next segment when it looks ok.

For a shallower mould (< 1cm) I drop T2 down to 638.

[Shades of Colour]

i haven't tried slumping 6mm thick glass but the schedule I use is

Rate - Temp - Hold
200 - 520C - 25 mins
330 - 660C - 20 mins
full - 516C - 50 mins
60 - 370C - 0 mins

Not sure if I'm helping or confusing with so many other schedules !!!

[Trudi]

Oh wow - thank you for all the replies!!

I put the kiln on this morning using the link from the website (Thanks Dawn .. trust me not to see that one). Fingers crossed.

It's cooling down now  - currently on 250°C

If that doesn't work I'll be checking out some of your other suggestions!

[JKC]

Hi Trudi
Hope it works this time.  When I went to liquid glass they gave us a handout with firing schedules for bullseye, full fuse, tack, slumping, fire polishing, small jewellery pieces and some for float, I could type it up and send it to you if you like.  Janet

[Trudi]

Ah bless you Janet

I'll see how I get on first - save you all that work!

Thank you xx

[Trudi]

Hmmmm - well it slumped about half way - so I'm going to have to have a little think!

[Shirley]

Same temp for longer?

[Trudi]

This time I tried

200-520-25
330-650-20
AFAP-516-50
60-370-0
100-40-0

as opposed to
RATE TEMP HOLD
Segment 1 167°C ( 300°F ) → 663°C (1225°F ) 10 min
Segment 2 999°C ( AFAP°F ) → 482°C ( 900°F ) 60 min
Segment 3 56°C ( 100°F ) → 371°C ( 700°F ) End

[Zeldazog]

Trudi,  when I referred you to the sheet, it wasn't for the firing schedule.  Below the sample schedule it says: 

Variations of slumping temperatures depending on size and shape

(Small deep moulds need higher temperatures than large shallow moulds).   

[Sarah A]

Hi I don't know what kiln you have but is it possible to view the bowl while it is slumping?  I put a long soak time when I first fire a new bowl and open the kiln periodically to see what it looks like and if it has fully slumped. I then not how long it took so I can program the kiln the same another time.