Crack sound and blue lines inside mug

[harlandraka]

Hi everyone,

When I remove the mug from my press, I can hear a little crack sound. The mug stays intact but I can see some blue shadowed lines inside it. Again, no breaks, no visible cracks, just those lines. I'm attaching some photos.

Do you know if it's a weird behaviour and what could be causing it?

[Justin]

Which mugs are you using? What press/time/temp etc?

[harlandraka]

Hi Justin,

AA grade orca coated mugs, 200 °C 201 seconds, high pressure... Press is a Chinese multipress

[InkExperts]

Hi, temp is a bit high and time is a bit long in my opinion. I use Orca mugs at 175-180c for 180 seconds. Although I have never been able to crack a mug as such through increased temp / time. Only other thing I would suggest is to ensure the mug is warmed before inserting into the press, this reduces a sudden change in temperature which can cause hairline cracks.

Alex

[Justin]

.... And remember you don't need a very high pressure, as long as blanket is making good contact with mug all the way around, it should close with just a little force.

[Fletcher]

Those lines are cracks. Did you sort it? if so what was it?

as already said Warm the bottom of the mug before pressing, Try reducing the temp and time. I use a chinese 5 mug press, temp is 170c for 160 seconds.