How to care for your letterpress plates
Store your polymer plates properly
To preserve your plates, the manufacturers recommend storing polymer plates in a constant humidity between 50% and 60%. At the very least, avoid extreme fluctuations in humidity. If stored properly (and cleaned correctly), your letterpress plates can last for one year or more.
- For your exposed plates, maintain a constant humidity by storing plates in a ziplock bag. Keep your plates away from ultraviolet light that will crack the surface of your plate (i.e. store in a drawer or cabinet).
- For your unexposed plates, store in a black light-blocking bag that is taped shut.
Cut your letterpress plates
Plastic-backed polymer plates are simple to cut: just use scissors. Easy. Fun. Done. Steel-backed photopolymer plates are not simple to cut. For the cleanest cut, we recommend using a metal shear or heavy-duty trimmer. You can also use tin snips, though you may end up with kinks in your plate, as tin snips won’t cut as cleanly. If we process your plates, we can cut your steel-backed plates on our metal shear-- just include a cutting diagram with your order. (To make a cutting diagram, use a line with a magenta stroke to indicate the cut lines on your file. Make sure to keep your cutting diagram simple, since we can only make straight cuts across steel-backed plates).
Change the adhesive on your polymer plates
As long as you're careful about not getting dust or debris on the adhesive, and you carefully replace the blue protective release paper after use, the adhesive on your letterpress plates should remain sticky for many years. Keep in mind that adhesive can always be inexpensively replaced.
Clean your letterpress plates
Step 1. Start to remove ink with a soft dry rag. If you are inking correctly, you should only have a thin layer of ink on the surface of your polymer plates. So start with a soft dry rag to lightly remove the letterpress ink. Normal shop rags, worn t-shirts, or synthetic printing cloths work well for cleaning the plate surface. A hard hand is not necessary here; a light stroke can remove most of the ink. Step 2. Wipe polymer plates down with a little mild solvent to remove the remaining ink. Choose a mild solvent. Printers who want to keep their photopolymer plates should consider a water-miscible solvent. Aggressive solvents that can clean lead type (like methyl ethyl ketone (MEK) or denatured alcohol) often dry out polymer plates, causing them to crack a few months later. Do not use alcohols. Keep solvents away from plate edges so that the solvent doesn’t contact the film adhesive. We recommend using solvent sparingly. Water-miscible solvents do not mean that you use water for washing your plates. It can soften and deteriorate your plates so they start to chip or crumble. Step 3. Wipe off your letterpress plates one last time with a dry rag. On all these steps, remember don’t rub too hard! The photopolymer is difficult to damage through scrubbing, but you should treat it like any typographic surface and not use too much abrasion when cleaning. Because you aren’t putting a lot of ink onto the plate relief surface, you can easily, but firmly wipe off the ink from your plates with just a light hand. Your polymer plates can last for several years if you follow these cleaning instructions (and also store your clean plates properly). If you’re not planning on saving your plates, just clean them with any normal press wash before recycling them.
Get rid of photopolymer plate curl
Like our skin, plates can be affected by the room temperature, humidity, and age. When humidity levels are low, the plates can look and feel brittle. With the passage of time, the thinner polymer on the plate edges are pulled towards the denser polymer text and images on the front—this causes curling. With a life expectancy of up to 1 year or more, polymer plates do age, but these simple steps can hydrate your plates and give them extra longevity. Step 1. Place your plate back in your platemaking washout system for up to ½ a minute (or, if you don’t have a washout unit, simply immerse in water). We suggest room temperature for a quick dunking. A ½ minute may only be necessary if your plates are severely curled. Step 2. Sponge off the water and place back in the drying oven of the platemaker for 5-10 minutes. If you don’t have a platemaker, use a hair dryer to warm the plate and make it more pliable. Placing your plate in a box and blowing the hair dryer into the box will keep the warm air more contained and warm the plates more effectively. Step 3. After the plate warms and starts to become more pliable, place the plate in its bag and set a heavy object on it to keep the flattened shape. This should help your plates relax so you can adhere them to your base for additional print runs. Here’s some final advice:
- if using a hair dryer, take care to avoid putting it too close to the plates.
- be patient, as warming the plates takes time.
- watch that you don’t handle your letterpress plates too roughly after the wash and during drying so your relief images don’t chip.
- remember to store your plates flat out of direct light and in a bag so that fluctuations in humidity don't affect the polymer.
- check your adhesive backing, to see if the adhesive needs to be re-applied to the back of your polymer plate for a secure hold on your base.