Magnesium or Photopolymer Dies.

When I get a plate made, I use wood mounted copper almost exclusively. I don’t order plates (from Owosso) often enough to worry about the price difference. Copper doesn’t corrode under normal storage conditions. Magnesium does very quickly without special precautions. Photopolymer requires that expensive base and, based on all of the comments I’ve seen, is much finickier about roller height and other inking issues.

Usually magnesium for me. I just store them in a bag lightly coated with Pam spray. Seals it. I have some that are over 50 years old.

Thanks for the feed back. We had bought a base for the Photopolymer and later switched from the standard back to the steel backed and did like the steel backed better. We have printed a few jobs on Magnesium dies both wood mounted and 1/4 inch mounted to our heat plate base (cold). We wonder if we can use the same die to print with as we would to do foil with. It is a strange idea but it allows the best of both worlds from just one die. Being able to foil or also print with ink colors and stock that foil color does not cover or a paper stock finish not conducive to foil. I guess I was not sure if one die can do both or if a print die is made the same way as a foil die.

Sorry I forgot one question. Which die type holds better detail Photopolymer, Magnesium or Copper. Also why one vs the other might help us pick which direction we choose under different job requirements.

I have used magnesium dies for 30 years and like other posters on this and similar threads, have printed with magnesium dies that are 50 years old. The problem I have found with them is not with the old ones, which have been stored on galleys without any lubricant coating and not in plastic bags, but rather with new dies that I have purchased in the last five years. These dies seem to coorode and grow fine “beards” much faster than dies made many years ago. I have tried to mend my ways and oil them and put them up in bags, but even these precautions have allowed some fuzz to grow on them. For that reason, I am strongly considering switching to cooper for my dies. I will have to pass the higher cost on to my customers, but for jobs I intend to reprint, it will be less of an issue. For a one-time-only die, I may still use magnesium, but I don’t do that much of that kind of work.

Jim DiRisio
The Norlu Press
Fayetteville, NC

Hi western411, I’ve worked in a shop making polymer, mag and copper cuts and to your question about if mag or copper dies are made differently for ink or hot stamping the answer would be no. The etching process may create a shoulder and depth that varies somewhat but they can all be made from the same negative and ideally should start out with very similar image potential. How well they hold up in printing or hot stamping will depend on the printing process, the press, the substrate and the care taken.
You would think that copper being the hardest of the three would last the longest but I don’t think thats always true. I’ve had metal dies get worn out quite quickly on a textured stock, others that seem to last forever, and I’ve printed 70,000 impressions with a polymer plate without any wear that I could detect so I think the overall question of which is better depends on the types of jobs you find yourself doing. Bruce

The better detail will be in copper, due to the way the metal etches. Copper etches straight down the sides, where mag etches with a shoulder that runs out at an angle. When the shoulders meet the mag won’t etch any deeper. With the copper verses polymer the copper is a harder surface that won’t loose the smallest details. Yes with the proper height base you can letterpress with .250 copper foil dies.

Thanks for the feedback. We are looking at the different ways of using our windmill as an every day printer much like the regular printing presses. With a standard printing press we used to use silvermaster for some projects or a neg and plate for others. We went to CTP a few years ago but we are looking at the same idea for the windmill. We want to adapt different types of projects to different plates as both cost control and project quality needs.

Bruce—polymer hot hot foiling is a different spec isn’t it….much harder??
I had believed so, but never used it for that……….

Jonathan I wasn’t referring to polymer hot stamping but to polymer for ink on letterpress. I’ve never used a polymer plate for foil stamping. I was speaking to this question;

“I guess I was not sure if one die can do both or if a print die is made the same way as a foil die.”

I wanted to make the comment that mag etched on 16g for type high ink or 1/4” for hot stamping is the same metal etched in the same acid bath. The difference is the thickness of the metal and the depth of the etch.

To clarify, Can the same Mag die be used for both printing and foil or is a different die needed for each due to plate thickness. I was not sure if I need a different thickness die to reach type high for printing vs foil. Our plan was to use our foil base using the same die different ways, some print (cold) and some foil ( hot). Will this not work?

There’s nothing about the plate surface that should prevent it working. The issue would be in getting a base of the proper height to have the surface be type high. You said that you have that so it should work. You also asked;

“Which die type holds better detail Photopolymer, Magnesium or Copper. Also why one vs the other might help us pick which direction we choose under different job requirements”.

clpx2 answered the part about which holds detail the best. But that leaves the 2nd part. If you really need to get the best possible image for every job then paying the premium for copper is it. But if some of the jobs that you print are short, one time only or or not particularly detailed then those might be some reasons to use polymer and save some money.

Thank you Bruce, I know it is a little odd to do what we want but working the cost vs use on some dies allows use to draw more work in. Also the extra utility of a die can make it easier for some clients to swallow the cost and time, while add to the final quality.

A comment from the UK. Having started letterpress printing in the 1960,s printing plates came in set ways. Copper was for fine Half tone printing and then there was zinc plates for line work and course h/tones, then there were stereos made of lead and nickle plated, also electros. By the 70,s we also had plastic plates and the first polymers which in those days were washed out with an alcohol solution. Now having gone back to letterpress printing using a windmill and a british built Miehle vertical. I am using polymer for both line and halftone work. The key to success is 2 fold, firstly get the polmers type high, I am using honeycombe mount and mounting the polymers on a lead or aluminum backing sheet and mount clips. Secondly is to set the rollers really accurately. This method allows me to print multi colour line work easily. This week I put on an A4 polymer on the Miehle and get a good print first pull. Also 7pt text caption on the windmill and the definition was great. So why not go for polymer. For a test piece earlier in the year I was printing a 4pp polymer plate that was 30+years old and still stuck down with the original double sided tape. Good luck with what you find most comfortable using.

Good Morning Frank, Thank you for the feed back. At this time all our work is on a Windmill. Part of what started this post was my own stupidity. We had entered into the foil world and had a foil die made. We discovered our heat plate was not getting quite hot enough and part way through the job shorted taking out the controller and a couple of heater cartridges. We are rebuilding the plate but had our Mag die and decided to print with it. Up until now we had only used photopolymer plates. That got me thinking (not a good thing) about the cross platform uses of Mag or copper dies and Photopolymer die uses.

Back in the early 90’s I ran a Miehle V50. One day I had a guy oiling it and he had the chase unlocked. He started it cracking the frame and off to the graveyard it went, I gave it back to the company I bought it from. That was long before the current demand for letterpress printing. Moving forward to today and as we have gotten into more letterpress printing we are wondering about the possible uses of a Miehle. How heavy a stock can you print and die cut and is it possible to get a hit on the stock like we can with the Windmill. I would love to hear any feedback you might have. I have wondered about adding a Mielhe again but have not found anyone running one to ask questions of.

Hi western411,
After a 40 year break of hands on letterpress l bought my windmill about 3 years ago and the v50 last year. The v50 was still being used commercially but mainly for cutting and creasing and occasional printing. I use the machines really to show interested people how letterpress printing was done in the 50’s and 60’s. The kind of stock I print on is usually mid range cartridge, coated stock for halftones and up to 250gsm coverboard, which I think equates to about 90 lbs. I am still gradually tidying up the press and it seems to get better with time. Not bad for an old girl of about 1955. As a book printer I have to own up and say I have never done any cutting and creasing only creasing and perfing so not able to give an answer on the heavy stock question.
Hope this helps.

The heaviest stock I’ve ever gotten through a Vertical (reliably that is) was 15 point blister board, with the grain parallel to the cylinder. Depending on the stiffness of the stock, one might go heavier, but I somehow doubt that there’d be much fun running 600 gsm Lettra through the press.