Coated or Uncoated Photoengraving Plate

The case for coated plate

The front face arrives with blue photoresist already applied and inspected for bubbles and scratches. You skip the coating step and the scrap that comes with it.

Coated zinc runs 0.8 to 3.0 mm in 1000 x 500 mm and 1000 x 510 mm. Coated magnesium runs 1.0 to 10 mm in 500 x 1000 mm, 610 x 457 mm and 610 x 914 mm.

The case for uncoated plate

Uncoated plate is bare metal, so you pay for the metal and not for the coating. If your shop already coats resist, that is the cheaper route.

It also goes further at both ends of the range. Uncoated zinc reaches 7.0 mm against 3.0 mm coated. Uncoated magnesium starts at 0.5 mm and reaches 2000 x 1500 mm, which no coated sheet size comes close to.

Surface finish on uncoated plate

SGZ polishes uncoated zinc from 0.8 to 3.0 mm. From 3.5 to 7.0 mm it is supplied non-polished, because that heavier stock is normally engraved or ground rather than etched.

Uncoated magnesium is supplied highly polished, with a smooth and shiny face and controlled thickness deviation.

If you are engraving rather than etching

CNC engraving does not use resist at all, so uncoated plate is the only sensible choice. SGZ's brass engraving plate takes this further: it is supplied unpolished with around +0.13 mm of thickness left on, so you grind the blank flat on your own machine first.

A simple decision rule

If you expose and develop but do not coat, buy coated plate. If you coat your own resist, or you engrave, or you need a thickness or a sheet size outside the coated range, buy uncoated plate.