marks on rock slate

[Justin]

I do slates for 500 seconds at 197c. Are you using any type of pad over them?

I also preheat for 125 secs

[pisquee]

We do 4 15x20cm slates per press (PressMech) at 180 degrees C for 480 secs (8 mins) Whilst they are in the press, the next four are sitting on top of the press warming up for the 8 mins. (The first four of the batch sit on top of the press whilst it warms up.)

Also, we use a thick rubber mat thing under the slates, and make sure that this is upto the 180 temp by closing the press on it until the temp read out gets up to 180.

Use InkTec's paper - don't think I've seen this issue on slates with it.

[GoonerGary]

I have had this same problem on cheap thin aluminium, but always blamed the coating when a drop in temperature didn't work.

What brand of slates/ supplier is everyone using?