mugs all crazing on the inside

[mrs maggot]

a customer has contacted me about some mugs i did for him, really happy with them, apart from some of them are crazed on the inside, and where the coffee / tea has stained them it shows up, i have not seen them yet as he is some distance from me, anyone else had this problem, they are BMS mugs, and we do normally dunk in warm water after pressing, they have shown no other signs of cracks - just a crazing on the inside only

[John G]

I had this problem when I used to cool them down using warm water, I kept a few test mugs for myself and within a few uses, they were all crazed inside. I stopped cooling with water, and use a fan now, since I changed I haven't had any mugs go crazy on the inside.

Cheers John

[mrs maggot]

yep i thought that might be it, have been fanning for a while now and these were part fanned part water (hubby finds it easier to get water than fan lol) i have told him will replace them

[Paul]

I have seen this before on my mum mugs! ones i cooled in water. even in warm water temperature is so different that cause surface cracking. never dunk them since. only fan cooled.

[logobear]

Fan cool?
We used to dunk em, - but sometimes heard slight cracking sounds, - and one or two lost a handle!
Now we just put them on the side until cold.
What is the advantage of force cooling - with water or a fan?

[JSR]

What is the advantage of force cooling - with water or a fan?

You sometimes get print bleed outside the print area while the mug is still hot. Sublimation continues until the mug temperature gets below sublimation temperature (140°C, if memory serves). Cooling the mug by fan or water gets the temperature below sublimation temperature as quickly as possible and prevents bleeding.

Bleeding is most common on the heavier mugs (11oz, 15oz, steins, etc) and mugs that are done in an oven (because the whole mug gets to the same temperature and so takes longer to cool down). It's less common on lighter/thinner mugs (like china mugs), particularly if they're done in a mug press (because the mug stays quite cool around the handle and center of the base, and so acts as a heat sink).

In certain circumstances, you may not need to force cool, but many people find it common practice to do them all - as in "better safe than sorry".

[gstk]

We just leave them to cool never had a prob of bleed

[mrs maggot]

i have it most on the big mugs, with black design on them

[John G]

As Laura said, happens to us with the big mugs and always black ink, sometimes it happens to the xpres Euro mugs, but this does depend on the time we give them.

Cheers John

[mrs maggot]

glad im not the only one john, the black bleed is a real issue on the big mugs - hence why we dunked them which seemed to work well, and they do not craze, but i guess we just dunked the smaller ones as well without perhaps the need to