Product Guide

What Is a Photoengraving Zinc Plate

Published 2025-02-10By SGZ Metal Material (Group) Co., Ltd.

A photoengraving zinc plate is a sheet of rolled zinc carrying a light-sensitive coating. You expose an image onto it, develop away the resist you do not want, and etch the exposed metal in an acid bath. What is left standing is a relief that can print, stamp, emboss or coin.

What the plate is made of

SGZ controls the alloy tightly. Aluminium sits between 0.02 and 0.10 percent and magnesium between 0.05 and 0.15 percent. Lead and cadmium are held at or below 0.005 percent, iron at or below 0.006 percent and copper at or below 0.001 percent. Zinc is the balance.

On the uncoated polished grade SGZ states purity as 99.95 percent. Purity matters because inclusions in the metal etch at a different rate from the surrounding zinc and leave pitting in the floor of the relief.

Coated or uncoated

A coated plate arrives with blue photoresist already applied to the front face, free of bubbles and scratches. You can expose it the day it lands.

An uncoated plate is bare polished metal. It suits shops that coat their own resist, and it suits CNC engraving, where no resist is needed at all.

Why the back of the plate matters

During etching, acid will attack any exposed zinc, including the reverse face. If it gets behind the plate the sheet distorts and the run is lost.

SGZ offers two answers on zinc. The first is anti-acid painting, orange or golden yellow depending on what is in stock. The second is a red film pasted on the back, which peels off completely once the plate is etched. Coated magnesium plate uses green anti-acid painting.

Sizes and thicknesses

Stock sizes are 1000 x 500 mm and 1000 x 510 mm, with other sizes made to request.

Coated plate runs from 0.8 to 3.0 mm. Uncoated polished plate runs from 0.8 to 7.0 mm, polished up to 3.0 mm and supplied non-polished from 3.5 to 7.0 mm.

What you etch it with

SGZ names Velv-Etch, the Fuji additive model E002, and its own house zinc additive oil as the additives its zinc plate is designed to run with. Both come in 20 kg drums.

The developer between exposure and etching is KY161, an alkalescent positive plate developer SGZ specifies as especially good for its own etching zinc plate.

What the finished plate is used for

SGZ lists banner, wall-calendar, printing, stamping, embossing and coining as the applications for its coated zinc plate. These are the jobs where a metal relief outlasts any printed or moulded alternative.