"Glenn" wrote in message
...
Never tried this but .. How about a big pavement roller? Lay the sheet on
exposed aggregate concrete or gravel and drive over it with that big steel
roller. Seems like it should stay flat or at least you could flip it over
and flaten it?

Folks keep recommending this method, but forgetting the top platen. You
cannot just hard-roll the sheet onto a pebbled surface, and expect to get
deep, well-defined textures.

Instead, place the sheet on the aforementioned aggregate slab (or make your
own with clean aggs on a clean, flat slab), then cover it with a single
layer of the same sized aggs. Then roll. The top and bottom aggs will
"nestle" within each other's gaps, yielding a heavy pattern.

You'll still have to do some flattening afterwards. But with both negative
and positive platens, you'll get deep embossing, and little "dishing".

LLoyd