Working With Polymer Plates

Posted on Thu, 19 Oct, 2017

An article by Chris Vasper

(originally from The Association of Hot Foil Printers and their Allied Trades Monthly Magazine)

As a company that sells used foil printers and polymer plate making equipment and uses polymer plates on a very regular basis, we often get asked about buying used plate makers from people who have, for whatever reason failed to master them.

For us it is so frustrating when polymer plates are misunderstood and misrepresented that I thought it was time to suggest some do’s and don’ts that may be helpful when making a polymer plate.

Firstly, use the right machine. Just because you have a UV light box, do not think for one minute that it will automatically be up to the job. We have used both the Printec machine and several of Polydiam’s and have found them to be excellent.

Some plate makers will have a vacuum facility and this will allow a really close contact between your vellum artwork sheet and the negative, absolutely vital when you are exposing those finer pieces of art work. If you are a beginner to plate making do not use very small type faces. Anything below a 10pt typeface and you should really be using a metal plate until you can become competent. The same can be said if your artwork has very fine lines.

When you mix your developer fixers make sure you use hot water in a ratio of 1 part to 4 parts water. This is to ensure that the water mixes well with the solutions and does not dilute too much.

Exposure times will vary from machine to machine but with both the Printec and Polydiam Machines exposure into the negative should be around the 20-30 second mark. Make sure when you wash the negative that it is wash in water in between the developer and fixer washes. Otherwise, the solutions will start to neutralise.

When closing the negative to the artwork and you are not using a vacuum facility, use some card board to add extra pressure. We tend to find that on average the exposure on the plate should take no more than 5 minutes but a lot will depend on the type of polymer plate you are using. We have always used the higher temperature 180-degree PPM/H100 from Polydiam with great success.

Scrubbing the plate can be fraught with danger. We tend to use a paint pad(Typical of the ones you can get from B&Q or Focus). The fine bristles on this sort of pad are ideal and we have never had a problem with them. This sort of pad also allows the washing to take place much quicker and therefore less scrubbing will not lead to an over scrubbed and ultimately, damaged plated. Whilst scrubbing, use a circular motion. After a while use a Stanley knife to cut around the area of the artwork and peel away the Polymer from the edged. This will also help to prevent over washing. Use hot water, the hotter the better.

DO NOT under any circumstances fill up a sink with hot water, place the plate at the bottom of the sink and start scrubbing. You will wash the artwork away very quickly and/or use so much water that when you put the plate on the machine, the letters will go milky and fall off. Use a steady trickle of water from a tap. Try and use as little water as possible. The plate at this point will start to froth slightly. All this is, is the excess polymer washing away. The nature of the frothing will change at the end of the wash to a very light look that just runs off the plate.

When drying the plate make sure you dab off the excess water with a cloth first and then using a hair dryer to give the plate a good dry and for at least 5-8 minutes. Within the first few minutes the plate will look dry but I can assure you it is not and to use it now would result in a lot of frustration. Do not be tempted to prop the hair dryer up next to the plate and leave it for the duration. It does not work and the plate would have dried unevenly. Keep the hair dryer moving over the design. I know it’s boring but trust me. Some people put the plate in an oven for about 5-6 minutes at about 100 degrees. I have never tried it but seems to work for them. I prefer the hair dryer method.

Remember to post expose the plate. I have lost count of the times people have failed to post expose. Again 5-8 minutes are ample.

Now hopefully all being well you now have a plate ready to print with. I find trimming the plate close to the artwork is useful as the heat is concentrated just onto the design and not on a lot of excess plate. When cutting the plate use a guillotine, if not a good pair of sharp, long scissors and try and remove the excess with single cutes. This will prevent excess bending which could cause problems when mounting the plate onto the machine.

You do tend to find that a bit of extra die bonding tape is needed to mount the plate on the machine if you are not using something like a clip-a-block system. Mounting the plate is best at about 120-130 degrees and then gradually turn the heat up to the required temperature. Do not put your plate on with the machine set at a very high temperature, otherwise the plate could again crack. Remember we have done a lot to this fragile plate by this stage so take it easy.

For best printing results we have always found it better to leave the plate on the printer for about 10-154 minutes before you attempt to print with it. This will give the plate time to settle after its washing, drying and 2 exposures. If you plate does not go milky white around the edges of some lettering at this stage, you should be ok. If it does go white then you have not dried it for long enough and may even have over washed it.

If you have just bought a printer and plate maker for the first time, always learn how to use the printer first. Become competent with using metal plates and type first. Only when you have mastered you printer should you then contemplate using the polymer plate maker. It is advice I have given time and time again only to receive a phone call 24 hours after the customer has taken delivery of the machine their first words are “I am trying to print with a polymer plate I have just made and I am having a few problems.” I do not know where the problem lies. Is it in their polymer plate making process? Or is it the fact that they still are unsure about the printing machine? It just makes out job a lot harder to solve the customer’s problems. I have often thought it a good idea that when a beginner gets a new customer, use a metal plate but practise with the same design with the polymer plate. In the end it all comes down to Practise! Practice! Practice!

As someone who has instructed on foil printers for over 10 years, we still occasionally get a plate wrong, but if you take your time, don’t rush, step back and think before you act then with a bit of practise you can quite easily master the art of polymer plates.

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