Rough edges, devit and discolouring

[chookie]

I have just made my second slumped dish, square shallow and small, from bullseye glass.

I put clear on the bottom, opal mint on the top and cut out a small strip from the mint to insert my own handmade pieces of clear glass with tack fused frit/stringer etc....

This piece was put to full fire on a layer of eco paper which has left a very rough bottom and edges to the glass. I thought that this would be fire polished off when it went into its slump firing...... it didn't
I also have devit where the clear patterened pieces were placed, ontop, hazy and horrible. There is also a bit of yellow hazing around some of the clear bits.... not so nice...

What can I do to smooth off the roughness, can i refire this piece? What schedule could I put it on?

Using devi spray in the future, will it really help?

[Zeldazog]

It would help firstly to know the two firing schedules you used.

Several things can cause devitrification, including not being meticulousl about cleaning your glass, but also holding too long at the higher end of the fusing schedule.  Multiple firings can cause it - you said the clear patterned pieces had already been fired before?  Some glass colours are simply more prone to devitrification.

As for the texture on the surface, fire polishing happens at a higher temperature than slumping normally does - slumping is the lowest temperature of all the processes, apart from annealing of course - so, if you want to fire polish - so, if you need to fire polish something, you need to do that before slumping.

I don't know what you mean by eco paper, but the rough edges, if it's what I think, could be caused by several things - possibly the texture of the paper, possibly needling.

Could you post a photograph?

[Zeldazog]

I've never used devit spray, so can't answer that one.

[chookie]

The patterned pieces were full fused....ah! Then cut up and then full fused again and then slumped... maybe that's why 

222c - 677c - 30 mins
333c - 804c - 10 mins
AFAP - 516c - 30 mins
83c - 371c - 00 mins
AFAP - 21c - 00 mins

Slump:

166c - 638 - 10 mins
AFAP - 516c - 1 hour
55c - 372c - 00 mins
AFAP - 21c - 00 mins


Ok, maybe now I know why I have the dreaded white scum nasties!

But the roughness is still there, I used Eco fibre paper that is quite rough and used it because it's cheaper. It has caused rough edges and underside too. It doesn't fall apart into dust like bullseye paper, it stays in one piece but falls apart when it hits the bin. You can use it for kiln carving too. I can use batt wash the next time on top of it to stop the roughness, if I use it again for anti - sticking that is.

I have been told to sandblast and then refire by Bullseye but I have no such equipment at home  Can I refire the piece on the ceramic slumping mould on a tack fire to get rid of the rough bits?

Thank you Z 

[Zeldazog]

Sounds like Eco Paper is what I know as a ceramic fibre paper - and it does leave quite a texture.  But it wouldn't bother me if it's on the underside?

If you've got roughness on the sides/edges, you could consider buying a diapad - diamond hand pad - they're about £12 each, take a while, but a much cheaper option than a grinder.

Sand blasting is the normal recommendation to try and get rid of devitrification on the surface - maybe try etching fluid/cream?  I don't know if that would cut deep enough to remove the devit though.

If you try and fire in a mould, above the highest recommended slumping temperatures, you are likely to get distorted edges.  I tried it once, trying to get a fire polish and slump at the same time.... got a very interesting wobbly edge effect, sadly only on three sides though!



Edited to add, just seen you actually referred to it as eco fibre paper in your last post, sorry missed that bit!

[flame n fuse]

I'm not clear whether you fused and slumped as separate programmes (as recommended), or not.

If you look at http://www.bullseyeglass.com/images/stories/bullseye/PDF/TechNotes/technotes_04.pdf
BE recommend cooling to a lower temperature than you have been using, to reduce devit problems. This might help (482, not 516).
If I run my kiln to BE recommended progs, I frequently get devit - esp with opaque blue. I don't know whether my kiln temps are accurate or not, but usually run programmes at lower temps. There is a lot of discussion on the Bullseye forum regarding problems with fibre paper, cleaning glass properly, hazing etc. Worth a look, but never clearly resolved.
You don't need to put bat wash on top of fibre paper, just put it on the shelf, or mould - and you can polish it a bit to give a smoothish finish.

HTH
Julia

[chookie]

I understand that you don't need to batt wash but I have read that you can, I just bought it after reading that you can use it as firing paper but didn't realise that it was rough   I normally use Bullseye but scrimped...badly!

Julia, the piece was full fused and then slumped, so 2 separate firings were done. The insert glass was fired full previously but I should have tacked it first.

Looks like devit is my main problem now, I don't mind experimenting with the rough dish, it should be a learning curve and it didn't cost that much to put it together. It's very rough though, I couldn't leave it as it is if I wanted to use it, I hate the feel of it.

Maybe I will see what happens in a tack fuse or smash it up and use the bits, I don't mind what happens to it... all in the name of glassy science.

I thought that leaving it at the 700 mark too long caused devit the most, when the glass is just below the point of becoming molten?

I hate the devit the most. I hear that devit sprays can leave spots and marks and all sorts, doesn't sound ideal.

[Zeldazog]

I have to say, I try to avoid using a colour on the top if I can help it; I usually cap with clear as I never get it with that.

I recently did a panel with a beautiful opaque blue top layer, which I couldn't cap as the design didn't allow in this particular case - I was rushing a bit, so I don't think I cleaned it properly and I got the dreaded devit.   



In terms of shelf paper, if you're really after saving money, why not use batt wash instead, - takes a little longer, as obviously you have to clean down a re-coat the shelves, but you can get a really smooth finish and it's many many times cheaper - a tub costing £5 will do around thirty 20 inch shelves - using thinfire it would cost something like £54 to do the same number.

[chookie]

I have batt wash already, I just didn't realise the eco was so rough, never mind, I shall use it to kiln carve with instead. I couldn't clear cap either as I had cabs on the right hand side of the piece to balance the inserts on the left.

I have just looked at Bullseye and they say that the pre rapid heat soak is optional, I have a lady helping me at their company and I'll see what she says. Maybe my 804c for 10mins can be taken out... plus I need to clean with window spray and paper towels, not detergent.

I'll post what she says as it may help others with what I have been getting wrong.

[flame n fuse]

Hi Chookie
I can understand your frustration!

Do your programmes with this kiln usually work OK - is this a new problem?

I think that BE suggest that you can cover up devit using powdered clear glass and another firing. I have never tried that and would prefer to avoid the problem in the first place. I'm not sure whether further experimentation with the ruined dish will provide any answers. I have found that polishing pads are useful for getting rid of the occasional rough edge, but never succeeded in removing significant devit with them.

could you run a small test piece with the same colours, but at lower temps to see what happens? our max temp for full fuse, in our kiln is usually 770, or 780C
Julia

[chookie]

It's the biggest pain and I have always has this problem, it makes things look amateur doesn't it  You go to all that trouble of making the design look great, only to have that horrible frosting in places and you don't get what you imagined it to be.

I shall have to see if the pre-rapid soak can come down in temp as you say and crack the door to cool down to the rapid cool AFAP.

Fun and games eh!

Thanks everyone

[Zeldazog]

I have found that polishing pads are useful for getting rid of the occasional rough edge, but never succeeded in removing significant devit with them.

I was only suggesting the pads for the egdges; the ideal scenario for trying to remove devit before refiring is the have a uniform surface finish - just removing the devit bits doesn't work.  The blue panel I did, I got someone to sandblast it all over, re-fired and still got devit - I guess the crystals go deeper than the level of glass that had been blasted away.


Chook, I'd only suggested using battwash as the separator because you mentioned earlier that you'd got eco paper as it was cheaper than Bullseye - can I ask where you got eco paper from, as I do use ceramic fibre paper anyway, and plan on using it more for some ideas I have.

[chookie]

I purchased it from here:

http://www.ebay.co.uk/itm/5-Large-Sheets-25cm-x-25cm-of-1mm-Eco-Fibre-Paper-for-Kiln-Fusing-Glass-FP05-/150755647734?pt=UK_Crafts_Glass_Art_Supplies_CV&hash=item2319bca0f6

'This is a one use paper and for a perfectly smooth bottom on your glass, should be used with a piece of thinfire paper between the fibre paper and your glass' - D'OH!!