Firing Schedule for floatglass

[bendytanya]

Hi here. I am still very new to glass fusing and have a Hotstart Pro Skutt kiln.  I have has some lovely successess with Bullseye glass but now I have been given a large amount of new float glass.  I eventually gained the confidence to unlock the advanced programmes on the kiln a few weeks ago but I cannot find a programme that fuses the glass completely and I am not confident enough to make my own yet.  The nearest I have found is this in farenheight:

1. 500/hr   to 1000  10 min hold
2. 500/hr   to 1725  60 min hold
3. 9999/hr to 1025  15 min hold
4. 9999/hr to 1000  30 min hold
5. 9999/hr to  950   45 min hold

I used copper oxide between 2 x 3mm 8inch circles and the copper powder actually reacted this time with this setting and the glass started to round the edges but it was still visable where I broke the glass in the middle prior to putting it in the kiln and the outside edges needed a lot more work.  All the other firings I have tried for float glass merely tack fuse.  Pease could someone tell me which parts I should increase as I really dont know where to start?   

Thank you for your time.

Tanya

[Zeldazog]

Have you tried the schedule that Naomi posted when you asked a similar question in another thread:

http://www.frit-happens.co.uk/forum/index.php?topic=60.msg430461#msg430461

It's a good starting point.

If, what you did wasn't hot enough, just add ten or 20 degrees and fire again.  

[Zeldazog]

At the top of this page is a useful temperature and rate converter, if you're used to celsius:

http://www.warmglass.com/phpBB/index.php

Remember to use the two different converters for temperature and rate.

[bendytanya]

Yes I tried that one.  Which segment do I add the 10/20 degrees to?  Its a bit confusing still!
Thanks

[Zeldazog]

Add the increased heat to the process temperature - which is the temperature that things actually happen at.

Take a look at these:

http://www.bullseyeglass.com/education/ - although the tip sheets and tech notes all refer to Bullseye glass, when you read these and understand what is actually happening at each part of the firing schedule, it helps you understand where and how to alter your schedules.

Incidentally, that schedule that you posted, the process temperature (2 in this case) looks WAY too high to me - 1725 deg F coverts to something like 940 deg C.  And I am not sure about the annealing either, that doesn't look right as there is no slow cool down.

[bendytanya]

Thank you for your reply.

I must be doing something very wrong then as when I did use the firing schedule I posted earlier, segment 2 was up to temp 1725 degrees f and held for an hour and it still didnt do much more than a tack fuse (although the edges has started to round).  I have read the tip sheets from your link (thank you) and I also have many books that I have read.  Could it be the float glass I have been given just will not actually fuse properly? Or should I go higher or try holding for longer first?  I am not trying anything I want to keep, just test pieces as you suggested.  Does the hold time have a big impact?  Still confused, but you have clarified some of it for me.   Thank you. Tanya

[Zeldazog]

I think you have already reached the max temperature for your kiln , but no float glass I have ever used has ever needed that much firing, it's way way over normal float fusing temperatures.

The hold and the process temperature work together - sometimes, you might want to hold for longer, at a slightly lower temperature.  Other times you might want to go slightly higher and not hold it for so long.  There are no absolute rules.  The main issue with long holds is how long you are in the de-vitrification zone.

Try following a standard Bullseye schedule and add 20 degrees or so to the process temperature - leave everything else the same. For now, forget  bubbles and inclusions, and everything else - find out the optimum working temperature for your glass and your kiln then work from there.