Magnesium Photoengraving Plate

PRINTING PLATE

Exposure

Halftone screen “9” is OK to obtain a correct exposure. For fine form, “11” is enough.

400-600mJ/cm2 is required for exposure.

Development

Put the exposed plate into 1% sodium hydroxide (NaOH) aqueous solution for 8-10 seconds, or into 5% sodium carbonate (Na2CO3)

aqueous solution or Hydro-Solve developer concentrate for 1 minute, in temperature 300C,then take out the plate from the solution,

wash and wipe it with sponge in clean water softly.

Repeat above step to develop again if the plate is not clear enough.

Then dry it with compressed air or by absorbent paper.

A faster developing will happened while the solution was heated.

Touch-Up

Touch it if necessary, no “Burn-in” is needed.

Weight

Record the weight in log.

Descum

Put the plate into 3% Nitric acid (HNO3) aqueous solution in room temperature and brush it lightly, then wash it with clean water.

Protect

To prevent oxidation, uniformly wet the plate immediately with Express Guard plate protector or Arabic gum aqueous solution before

clamping it on the lid of the etchin machine.

Etching

Follow the instructions by the machine producer to etch the plate.

Bath formula: Nitric Acid 41.8oBe’ 19% by volume

etch Additive 4% by volume

water 77% by volume

Machine data: paddle Depth 8-10mm

paddle speed 380 rpm

starting temperature 28oC

working temperature: 35-40 oC

plate holder 6-8 rpm

Etching speed: 1mm per 7 minutes for a new bath

The paddle speed and starting temperature should be adjusted according to the variety of the sidewall in the following etching process.

After etching, wash the plate with water or tri-sodium phosphate aqueous solution, then dry it.

Replenish acid

Weight the plate to calculate the magnesium dissolved, then replenish Nitric acid accordingly, about 160ml Nitric acid corresponding

1 ounce of magnesium. Do not forget to check the dip gauge.

Top removal

Soak the plate in a 10% sodium hydroxide (NaOH) aqueous solution or in top remover concentrate solution in temperature 30OC

about 3 minutes, then remove and brush it with water.

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