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Knowledge Base

Posted on 29th June 2011
Comments (32)

Warm Glass Learning LogoWelcome to the Warm Glass UK - Knowledge Base.

Got a question about glass work? Want to share your knowledge? Want to engage with fellow glass artists? This is the place to do it!  Post any questions or tips you have in the comments and start a conversation with your fellow glass artists. Warm Glass Staff stop by regularly too, so we will be happy to post a reply too!  Get involved!

Don't forget that we have loads of tips elsewhere on the site. Click here to find links to firing schedules, tip sheets, videos and more!

We look forward to hearing from you!

- Warm Glass Team

Mark 30th October 2013 12:43pm
What is the best temperature to fire Bullseye Glass to?
Connie 30th October 2013 12:55pm
Which cutter is best? Pistol grip or pencil grip?
Warm Glass 30th October 2013 1:14pm
Mark, in reply to your question: What is the best temperature to fire Bullseye Glass to?

We generally fire a full fuse to 804C - full details of firing schedules are accessed from the 'Help' section of the Warm Glass site. Hope this helps!
Warm Glass 30th October 2013 1:16pm
Connie, it is simply a matter of personal taste. Some prefer the pencil grip while others like the pistol grip. We use both types regularly here at Warm Glass
Sue Mclaren 17th February 2014 9:22pm
How do you use glass line paper?
Kirsty Dale - Warm Glass UK 24th February 2014 10:52am
Hi Sue, sorry for the delay in replying to your query!
Glassline paper can be fused between glass layers to add interest to your work. There is a tipsheet on how to use it here:
and you can look at some images of students' work using the paper on our 'Get Going with Glassline' course in our gallery here:
I hope that helps!
Hazel 25th February 2014 10:51am
Silver Wire Question:

Hello I am thinking of trying to make my own bails and fusing in between the glass. I have looked at the silver wire and there are two sizes, 0.7mm and 1.00mm.Can you let me know which would be better and it will not tarnish in the kiln? .also how to secure it straight before I fire.. Thank you for your help. Hazel
Simon - Warm Glass UK 25th February 2014 10:55am
Hi Hazel,

Both the 0.7mm and the 1mm can be used between glass and it really depends on what thickness will look best with you pieces. I prefer the 1mm.

All silver will tarnish a bit and this can be removed with silvo or vinegar. The silver we sell is 999 pure and therefore will tarnish less than sterling silver. Please be aware that silver will react with some glass types.

This section of the website contains more information: Glass
Bridget 25th February 2014 11:34am
Marks In Glass:

I'm putting together a composite piece for a kitchen splashback. All the items have been constructed and now I'm fusing them.

The first piece has fused. It has come out of the kiln with this very strange effect. It looks like an inclusion below the green and on top of the clear. The green is rippled but I don't think it's an air bubble and so shows although the black is not breaking through. The clear is smooth but clearly showing as black.

The kiln cycle is standard with a maximum temperature of 804 and has been used a number of times before. I.e I didn't set it for this cycle.

The piece is glued however the glue was not positioned where the black is.
Do you have any ideas?
Simon - Warm Glass UK 25th February 2014 11:35am
Hi Bridget

If the black looks silvery and flaky, inside a bubble, it is glue. The glue burns off and tracks to the middle of the glass. Glastac glue will reduce but not eliminate this happening, the best thing is to not use any glue or use glasstac sparingly and near the edge of the design.
Geo 3rd March 2014 9:55am
I've been trying to find out how to make electrodeposits of copper on a glass surface. To make the glass conductive I believe painting/praying Electrodag on the glass is one way. Only snag is that it comes in 1.5Kg tubs at ?1190! Does anyone have knowledge of other ways to achieve metal plating on glass?
Simon - Warm Glass UK 3rd March 2014 10:51am
Hi Geo
It's out of our field really, it depends on your application, but you can fuse copper wire between sheets of glass which would be conductive. Otherwise I imagine that a foil cut on a digital die cutter. Best of luck.
Carol 3rd March 2014 1:54pm
I Have made some placemats using bullseye fused glass 2 layers. How tough and heat resistant will they be?
Simon - Warm Glass UK 3rd March 2014 1:59pm
Hi Carol,

Bullseye glass is as strong as most other glasses but is not toughened or heat resistant like Pyrex. Assuming that the glass has been annealed properly Bullseye glass can be used for placemats, plates, bowls and coasters without issue.
Mandy 25th March 2014 1:42pm
Hi there. I have been using fibre paper to cut shapes then use my 'waste' glass (the very small pieces). This works well but obviously I can only get one firing per piece of paper. I have noticed the fibre hardener on your site. . If I was to soak the fibre paper in this product, would i get more than one firing with each 'mould' ? Many thanks.
Simon - Warm Glass UK 25th March 2014 1:45pm
Dear Mandy, Yes the hardener will make the fibre hard enough to use for repeated firings. However, you will need to use Primo primer or Bullseye shelf primer on the form to allow the glass to cleanly release. You can also use iridised glass against the mould for a clean release. Kind regards, Simon
Gerry 25th March 2014 1:47pm
I would like to glue glass to glass. What glue do you recommend that dries clear?
Simon - Warm Glass UK 25th March 2014 1:53pm
Gerry, There are several options for gluing glass to glass, the simplest is silicon and aquarium silicon is the clearest. Single part silicon is good for gluing large areas together. The professional laminating glues are available from Bohle and you can either use 2 part silicon glue or ultra violet curing glue, both are very strong and very expensive. Simon.
Sarah 26th March 2014 10:14am
3mm fibre paper - I used this to line my shelf and did a full fuse kilncare hobby fuser programme 3 setting. When finished the underside that has been touching the paper has come off but has left a rough white consistency on the glass which does not come off even after brushing under running water. Please could you advise what I am doing wrong? The base glass has been opal coloured - black, red and also some coasters in clear. Many thanks
Simon - Warm Glass UK 26th March 2014 10:28am
Dear Sarah

3mm Fibre is not suitable as a separator for fusing as it will stick to glass in certain circumstances. Fibre is used instead of a shelf by some people and when used in slumping will release, it can also be used in casting to form a barrier; generally opal glass will stick to fibre worse than transparent glass.

The specific preparations for separating glass from the shelf are Thinfire Paper and Bullseye shelf primer.

Bullseye tipsheet about fibre paper:
Bullseye thinfire paper:
Elaine 26th March 2014 10:44am
Hi - On a course I attended some time ago there was the opportunity to screenprint. I have recently tried printing again using the Sunshine enamels and the oil based mixing media bought from yourselves. Despite mixing different consistencies the mix becomes almost solid on the screen and requires strong chemicals to remove it. Using it too frequently would I think end with damage to the screen. Looking at the safety sheets for the water based mixing media they are the same NR221. What is the difference between them and which would most likely have been used on a course? Many thanks.
Simon - Warm Glass UK 26th March 2014 11:45am
Elaine, Thank you for your question. We now use the water based medium in the studio for exactly the same reason you suggest. Whilst the consistency of the oil based is slightly nicer to work with, the cleanup is very time consuming and strong chemicals are required. The water based medium just washes off with water and a bit of detergent. I would personally use oil based medium for painting and water based medium for printing.
Jennifer 26th March 2014 11:53am
My square earring pod mould broke on firing. I used primo primer, 4 coats, and put the mould on a kiln shelf, the kiln was cold to start off. Set the kiln to 8.70c full speed for 10mins, switch off kiln, open door leave to cool to 5.50c shut door and leave until reaches room temperature. The break had occurred in the first ten 10mins. Why?
Simon - Warm Glass UK 26th March 2014 11:56am
Jennifer, I am sorry to see that your mould has been broken during firing. The speed of your firing has caused the pod mould to crack through thermal shock. The 'full speed' setting is really only appropriate for small pieces of jewellery and whilst the glass could have taken the heat, the mould could not. The PDF on the product page has a schedule which would be appropriate.
Angela 1st April 2014 11:32am
Can you advise why the silver wire I bought recently seems to be causing a golden glow around it when used as an insertion? I've tried it with and without glue to fix and both ways it still leaves a pronounced yellow hue in an area around. Many thanks
Simon - Warm Glass UK 1st April 2014 12:23pm
Hi Angela, The golden glow around the silver is silver oxide which will always be present in silver, if you clean the silver with vinegar before use and try Crystal Clear 1401 as your clear cap, you will be reducing the possibility of this happening. Naturally, if you want a reaction you can get impressive reactions with glass such as French Vanilla and the reactive glasses.

I hope this helps.
Leighann 2nd April 2014 10:52am
I'm being a bit adventurous and going to attempt using my new drop ring mould this week, fingers crossed it works. Was just wondering whether I really need to flash vent? All the research I've done talks about flash venting if you do a deep drop. Do you have an example of a firing schedule? Otherwise I was going to start with the one on the website linked to the mould.
Simon - Warm Glass UK 2nd April 2014 1:07pm
Hi Leighann, The dropout schedule on the site will work, but to be honest a simple 167C to (650-700) with a long hold will work just as well. I have just uploaded some top tips on the dropout ring product pages.

Our Top Tips:

? The blank should cover the outside diameter of the ring but not hang over the edge
? For drops under 10cm the optimum thickness of the blank is 6mm to 9mm
? For drops over 10cm the optimum thickness of the blank is 9mm to 12mm
? Fire the blank on a basic full fuse and anneal correctly for the thickness of the glass
? Use Bullseye separator on the dropout ring and also 1mm fibre, cut 3mm back from the ring edge
? The optimum top temperature is 650C to 700C depending on your kiln, glass thickness and how much you want to drop
? In plugin kilns remove the shelf for longer drops but remember to protect the base of the kiln with fibre paper

You do need to cool the glass rapidly to stop it dropping ? this is done when you can see the glass has dropped to the point you were hoping.
Tim 15th April 2014 12:51pm
Band saw cuts leave devit on 3mm thick glass. Tried Spray but it still leaves a line?
Simon - Warm Glass UK 15th April 2014 1:05pm
The devit from grinding or cutting can be reduced by keeping the piece wet and cleaning the cut with a toothbrush under a running tap ? this gets all the loose bits out of the cut. Then fire the piece onto shelf primer rather than thinfire as the smoke from the thinfire helps to kick off devit. If you fire at 333C ph between 677C and 804C this will also help. Good luck!
Lizzie 3rd September 2014 12:19pm
Hello I have just bought a white and green Sunshine Enamels along with the water based medium to have a try but I am unsure if the piece should be prefired before topping. Also does it need to be completely dry before firing? Thanks.
Simon - Warm Glass UK 3rd September 2014 12:23pm
Hi Lizzie, The Enamels we sell mature at 750 - 810 degrees C and therefore can be used in a full range of kilnwork. There is no need to prefire before applying enamels. However, the lower you fire the enamels (within the maturing range) the stronger they will come out. Prefiring layers before topping is not essential but will help to reduce potential bubbles.

Enamels do need to dry before firing, or they will blister badly. Sifting a very thin layer (2 grains thick) of clear glass powder over the enamels can help achieve a smooth glossy finish and will also reduce bubbles if sifted between layers.
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