How do I create a "soft" tac fuse

[Bluebell]

Hi everyone

Well, I'm away to take the plunge and have a play with my kiln......about time!

I want to create a dish with a bit of texture and I thought about having some clumps of crushed glass on it as a feature.  The idea I have, is to have very soft lumps rather than sharp edges.  The dish is in the kiln just now doing a full/fast fuse to get the 6mm thickness and I thought I'd put it in for a second firing on a tac fuse so that the crushed glass doesn't fuse away into the main glass, but I don't want any rough edges, more like raised lumps.  Am I going about this the right way?

So, if I put it in for a tac fuse, how much should I raise the heat to give it this rounded look?  I've got a Hotstart Pro.

I hope this is making sense! 

Cheers x

[Sarah]

Hi Linda

Have you tried the Bullseye website? They have all sorts of useful info and its the first place I look for help with fusing.

Have a look at the quick tips on frit balls  

Sarah
xxx

[Hazel]

You need to pre-fuse the rounded bits you want for the decoration seperately first, then tac fuse them onto your base glass.
As Sarah said - go to the Bullseye site - it is brilliant for tips and projects. Good luck and have fun!

[Zeldazog]

All good advice

I would also do a test firing with a small square of glass and a couple of bits of frit - all kilns are slightly different, and you need to find the optimum temperature that yours will do this at - so it's difficult to give a definitive answer as to what temperature to tack fuse, as it's a combination of your kiln, what temperature, and what hold.

(I take it you're using it in 'Glass Fire' mode, or whatever it's called - I put mine straight into full programmable when I got it, so I have never actually used it!)

Better to waste 5 units of electricity than find you've overfired your bowl 

[Bluebell]

Hi

Well, I took your advice and did some test pieces - large pendant sizes.

Now the programmed temp (Hot Start Pro - automatic) is 1325F and I raised it a little to 1350F with a 10 min hold.  Before assembling my "bits" I crushed up a few bits of glass (thick poly bag and hammer style) and sprinkled a little on my test pieces.  The biggest pieces were only about 2/3mm.

Result - they're bonded and stuck firmly, but when I run my finger over the top, I still feel that they should be a little bit smoother.  There are too many hard (not sharp) edges. 

I also did a couple of 2 x 4cm (3mm) with a pre-fired small cab that I made months ago.  They came out ok, but again I though the edges were too hard - they could do with a slight rounding.

Now my question is......should I go hotter - say 1360-1370F or should I keep the temperature, but hold longer to about 15-20mins?

Does this make sense?

I've not played with my kiln ever - I always use it on auto so this is quite an adventure for me!

Thanks x

[Zeldazog]

Glass, like ceramics, isn't just about temperature - its about "heat work" which means a combination of how hot, and how long and set temperature.

You will probably find a similar result whether you hold it for longer, OR take the temperature higher.  I personally would try altering one to see if it works.  If still doesn't work, then add to the other.  Just don't do both at the same time, or else you won't know which one worked best!

You are looknig for quite a specific result, using your kiln, and the only way to find the answer is to experiment until you get the desired effect.

[Flippopotamus]

1350F (or 732C in English!) is right at the edge of the Bullseye devit zone.  Generally hanging around between 730 and 760C (1350 to 1400F) should be avoided due to devit potential.  Once you've fully fused a piece you can't undo it, so if you have the patience I would try a longer soak at 732 first (though I'm not convinced this would work sufficiently), and if still not right, go for a 5 or 10 minute soak at 760 (but remember you have to go through the annealing cycle every time, and should really increase the anneal soak time every time a piece is re-fired.

The Bullseye Heat & Glass Techsheet (http://www.bullseyeglass.com/pdf/technotes_tipsheets/TechNotes_04.pdf) is well worth a study

Flip

[Zeldazog]

Once you've fully fused a piece you can't undo it, so if you have the patience I would try a longer soak at 732 first (though I'm not convinced this would work sufficiently), and if still not right, go for a 5 or 10 minute soak at 760 (but remember you have to go through the annealing cycle every time, and should really increase the anneal soak time every time a piece is re-fired.

This is one of the reasons I suggested doing test firings, rather than risking over firing the proper piece AND as you say Flip, the increase in annealing that would be required.

I remember someone, I think Dennis Brady, posting a while back that after being fired four or more times, the glass becomes less stable.

And I talk in centigrade too! 

[Bluebell]

Hi

Thanks for the advice! 

Sorry I'm in Fahrenheit!  The kiln was delivered that way and that's its language!  I have to stress that I don't know too much about the technical side of the kiln - it's automatic - I just press the button and it does it's thing.  It's programmed to do the whole works so I'm not familiar with the advice of "increasing the anneal soak time".  I know what it means but I've not had to do it manually on the kiln. 

I can tweak it a bit i.e. when I select "TAC" it gives me it's programmed 1325F and I can press an arrow button up or down to increase or decrease the temperature.  Same with the hold time.  The rest is done automatically.

Taking all the advice, I think I'll go for a longer soak time (mindful of the dreaded devit), so is 20 minutes too excessive or would 15 minutes be enough? 

I hear what you're saying about try a little and see, which I know is good advice, but I'm curious to know what you would have a stab at first.  I'll still be working on the test pieces and I take it it's ok to put the same ones back in the kiln ????

Many thanks!

[Zeldazog]

I seem to remember it was really easy to change the programmer to Centigrade, it was the first thing I did as soon as I switched it on - however, I can't remember how I did it and my instruction book is down at the studio - but you will find that most people talk in C's rather than F's on here, so if you can find the directions how to do that, it's worth doing.

And yes, personally, I'd simply refire the test pieces rather than keep using more glass

[Warm Glass UK]

It's really easy through the Options menu - if you call either Simon or Veronica when you are by the kiln, they can talk you through it.

Pippa