DSF

We've been printing glass coasters for years but sometimes find paper sticks after pressing. We either have to spend minutes washing them under water trying to scratch paper off or waste coaster and use another. Never figured out the reason. Bad coating? Too much pressure?

Any ideas folk?

If it helps we press glass at 190c 3.5min (210s) low/medium pressure with teflon sheet above and below with glass placed on press on top of paper of course (design not reversed). The design always prints perfectly but after cooling some coasters come away cleanly and others bonded to paper.

Sounds like you have kinda answered your own question there fella.
If your doing a batch of say 12 and 9 release fine but 3 stick, then it has to be the coasters surface has been over coated.

I used to have this with mugs. but only when using the truepix paper and dunking them in water.
I removed the paper before dunking and problem solved. Now I use the ink experts mug paper I don’t get this when dunking anymore so my issue was paper.

It is TruePix 24" rolls we use but then again never happens to glass chopping boards so perhaps it is the coating. It is so difficult to know from looking at a coaster whether this will happen and of course cannot afford to throw away stock. Will make closer inspection on next batch. Thank you.

Many moons ago I had a similar problem with random aluminium panels from Chromalux. I emailed them and they said it was moisture either in the paper or in a panel. Their answer was to preheat the panel just 10 seconds, put the print on, pause, then press. Well it worked. Why random panels would have more moisture I have no idea, or whether that was actually the problem, I have no idea, but it worked. Then I had the same problem with some big slates (I got some just short of A3), same problem, same solution.
I wouldn't be so bold as to say that'll do it, just passing on information.
Interesting I was using rolls of Trupix.

Janners

You will get moisture in the product depending on what time of the year it was produced. In summer, China gets very humid which can cause production to stop..these were metal panels being produced, but I'm sure it would also relate to similar products. Whose glass coasters were you using? There are generally two styles of glass coaster available.

Well we've found three types and the best ones that never cause an issue are sold by Neil Brothers but they are not getting stock until June at the earliest. We bought from that supplier we cannot talk about (LF) but sent them back as the quality of the print differed from coaster to coaster - We printed four from one pack and all four came out totally different. The current lot is from Signzworld which print nicely but 1/3 are sticking. I cannot see how we can easily pre-press glass as it is bloody hot so would need to let cool down before taping down which means the moisture could come back?

It's been a while since I've bought glass coasters, but Neil Brothers were cheap and fairly decent, but I discarded half of them due to missing coating spots and scratches on the upper side.

Bought from the 'LF unsupported supplier' many years ago, but immediately returned my order because my batch was crap.

Haven't tried Signzworld. Are they a glossy sub coasting or a dull thin matt finish?

Novachrome only sell the dull matt version unfortunately.

We print glass coasters at 180 for 4 minutes
Never had a problem with them sticking (though we do sometimes on slates)
Use Inktec papers
For coasters, we use heat gloves, and remove the coasters straight away after opening the press and leave them to cool upside down on a silicone mat

E2A - we've always done this method, and have printed glass coasters for years starting with the only ones we could find which were very expensive from TTP, and since now use much cheaper ones from NeilBros, LF, and DyeSublimationSupplies

That's interesting. Maybe we reduce the temp and extend the time for the cheaper coasters we are having to use. Will give anything a go to stop scrubbing them!

pisquee;147768 wrote:
E2A - we've always done this method, and have printed glass coasters for years starting with the only ones we could find which were very expensive from TTP, and since now use much cheaper ones from NeilBros, LF, and DyeSublimationSupplies

Do the DyeSubSupplies' glass coasters have a glossy coating? When I saw the 'pack of 4' on their website, I assumed they were the same as Novachrome's matt coasters.
[MENTION=4836]UK Printed Mugs[/MENTION]
I use a sheet of plain paper either side, a sheet of silicone above my coasters and print through the glass. My press usually requires a higher temperature, so 198 at 300s - 345s depending on the design. Trupix paper or InkExpress heavyweight.