antioffset spray on windmill

Can anyone tell me about how to use a liquid anti-offset spray device for a 10X15 Heidelberg windmill press?

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Hi Ross,

There is a glass jar, up in the area of the spray unit. one position (lower) for when not in use. Another higher position when in use (gravity feed), the bottom of the jar has a dowel shape that fits into this arrangement. The glass is to hold a liquid spray solution (about 10 years ago it could still be bought from Heidelberg, it will come blackish in appearance). I think sysco also sold the liquid spray in 5 gallon buckets. Messy stuff, be sure to wear a mask if you use it.

Anyway, the spray unit can be activated by partially closing a valve, down on the back of the air pump cylinder (standing in front of the machine it is on the right rear, down by the floor), at the bottom of it you will see a small screw affair that has a cap on it in the open position, screw this in most of the way, but not all the way, perhaps leave 6 points of space to start with. If not enough blast, close it some more. There should be a hose running up to the spray unit from there. On the spray unit top back you will see a knurled screw with a lock nut. Loosen the lock nut and turn the screw in for less solution to pass or screw it out to let more pass by.

These units let the solution out of the center and air is sprayed from the two holes on the side. So it is a mixture of air and solution you end up with to be sprayed on the finished sheet. Usually a little solution goes a long way. But that depends on the weight and coverage on the sheet you are printing.

Also, these unit are notorious for not haveing been cleaned the last time they were used. If so at the nozzle there is a screw ring holding it together. Unscrew it and soak in warm water for a while. The parts are made of brass or bronze so be careful. Perhaps gently with pipe cleaners or a light brass brush to shine them up and reassemble.

Be sure to clean up when done to avoid the dried up mess later. Good luck.

Calvin C.

Thank you for the response. This has been the most informative info I have gotten so far.

Hi Ross

When I used a wet spray on my Heidelberg 13x18, it was Gum Arabic

This is like the solution used for preserving litho plates

As the spray falls, it dries into a powder which then acts as an anti-set off spray.

If you can, try to change to powder, as the wet spray can be a health hazard


Hi Alan,
Did you use the Gum Arabic straight or diluted?

Hi Ross

I think it was straight, it was a long time ago, but you need to play around.

Try it straight first, and if it won’t spray, then dilute it carefully.

Make sure that you set it correctly so the spray dries before it hits the paper stack otherwise you will end up with a block of wood!

Try it straight and run some scrap paper

Hope this helps


I never got the spray going but I figured out that by using a heavy impression resulting in a slight debossing all set off can be avoided.