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Making photopolymer plates

Hi everyone,

I know this topic has been addressed but I’d like to ask something more specific about making photopolymer plates.

I just made my first plate at home yesterday using a small UV exposure unit. I washed out the plate by hand.

I got a good enough result for my first attempt. The design was for a business card and all of the details appeared except a line of writing with a very fine font. I washed that line away during washout.

My exposure time was 3 mins and washout was about 4 or five. When the plate was finished, it was very jelly like and squishy. I thought the plate would be hard in the morning and I was a bit but not enough for printing.

I’m using plates from Polydiam in the UK. There are called PPF-120. 120 is 120 mm.

Does anyone have any tips on how I can improve on my second attempt?

Kindest regards,

Rebecca

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It appears that lack of exposure might be your primary problem. Try doubling your exposure and see if things improve. Are you using slightly warm water for the washout? Five minutes seems like a pretty long time, but a lot depends on your particular brush and set-up.

The results you obtained also might be an indication that the plate material is old, but if freshly purchased, you would hope that would not be the case.

There are a few good You-tube videos on photopolymer washout using simple equipment, and you might check some of those out to see if you are working properly (although some of those may mislead as well).

John Henry

You mention exposure and washout times. That’s only half of processing, with drying and post-exposure following.
Drying is done with moving heated air (the lowest-tech method being a hair-dryer), and a typical post-exposure is twice the exposure time (but only after the plate has cooled from the drying step). Skip these steps, and a squishy plate is exactly what you get.
The Stouffer 21-step gray scale is a standard tool in determening plate exposures. It is used along with manufacturer’s specifications to determine the normal exposure time for a given plate material and lightsource. Different plates expose to different steps on the scale.
Once a normal exposure time is determined, then adjustments are made for problem images like fine detail (for which exposure is increased) or for solids or reverses (for which exposre is decreased). And many have solved borderline problems by simply under-developing the plate. You don’t always need to washout down to the base material.

Hello,

Thank you so much for your help.

I made a second attempt. This time I exposed the plate for 5 minutes. I did a washout for 3 minutes, the finest detail got washed away (it was thin lettering). The logo and the thick lettering appeared perfectly.

I then dried the plate with a hairdryer and then used the cool setting to cool down the plate. Then I put the plate back in the UV exposure unit for another 10 minutes.

The raised part is still a bit soft compared to photopolymer I have purchased that is very hard. Also the thick lettering dissolved a little and got thinner like it wore away.

Do you have any suggestions of what to try now? Did I do the post exposure for too long?

Thank you again for your help,

Rebecca

Hi everyone,

I made another attempt which has turned out much better.

All of the details are intact including the fine writing that I had washed away before. I washed away all of the unexposed photopolymer and the plate now looks like the ones I previously ordered from a professional plate maker in the UK. I’m in Ireland by the way :)

I dried the plate using a hair dryer. The plate is not so squishy now but if I put my nail very close to the details and drag inwards to apply a little pressure to the design, it squidges, it’s not firm. Sorry if I’m using very amateur terms to explain.

I’m afraid the plate won’t ever go hard though. The last plate I made, I assume I overexposed it because lots of the design has thinned and disappeared.

I just re exposed the plate for 2 minutes and it’s a bit harder.
The fine detailed part of design melted a bit. The details of that part were clear but not they look like they’ve melted just a little. The rest of the plate that has a chunkier font and a logo are fine. I’ll keep trying. Could someone please point out if there’s anything I missed?

Best wishes,

Rebecca

Hi Rebecca -

I’ve been making my own photopolymer exposures for a while now, and my first many plates were terrible.

It sounds like your plates are coming out like my initial attempts - holding the larger areas, losing fine type in washout, etc.

Make sure you keep tabs on all the variables - the density of the negative, contact between the negative and the pp, exposure time, washout technique, drying, and post-exposure - seeing what works and what doesn’t.

You’re likely to see real improvement in your plates as you get a handle on all the variables. It worked for me and it will work for you too. Just hang in there are keep fine-tuning your process. Good luck!

Oh, and I should mention, are you using Kreen? It’s a translucent plastic sheet that disperses the light so you get a “shoulder” around your exposed areas.

Hello :)

Steve thank you for the advice. I’m not using kreen. Would that improve my plates? How would that improve the plate?

I just tried using the last plate I made in my letterpress. I tried to do a blind deboss with some cotton paper. When the plate met the paper it stuck to it and I had to rip the paper from the plate. Now there is fluffy paper stuck to the plate that won’t come off. I may need to post expose for longer.

Has that happened to you?

Best wishes and thank you :)

Rebecca

Hi guys,

Sorry for so many questions but I’m really trying to get my plates right.

I’ve made 4 now and I’m comparing them to see what I can learn. The plate that I exposed first for 5 minutes and later after washout and drying, I re exposed it for 10 minutes. That plate seemed to have gotten too much exposure because all of the design thinned considerably after being re exposed and the design when fine before re exposing. The problem is that the overexposed plate is still not hard and it’s still squishy which leads me to thinking it doesn’t matter how long I expose or re expose the plates, they will never go hard.

Also when I’m re exposing the plate, do I just put the plate alone face down in the UV exposure unit? The plate sticks to the glass and I have to peel it off.

Best wishes,

Rebecca

This is my exposure unit by the way -
http://image.made-in-china.com/2f0j00wSrTkZvyyRoO/Mini-UV-Exposure-Machine.jpg

Rebecca :)

Uh, I have it on pretty good authority that the kreen doesn’t disperse the light and make a shoulder. The actual lights used are what create a shoulder, and the fact that the polymer is so close it is receiving light at an angle, is what does it.
This is why tubes are recommended over point light sources by manufacturers and professionals in the field.
The close distance to the exposure source, which creates a situation where the light is not diffuse but rather angled, is what creates the ‘shoulder’ and for proper printing it should be about 70 degrees.

Kreene is thin stuff and couldn’t possibly diffuse the light enough to create shoulder, though it may contribute minutely (it being frosted). This is contentious at best though, and I apologize if I seem to be starting an argument- but the right information is key to achieving results.

Rebecca:

The second time you expose your plate, you needn’t put it under glass. (This is called (post exposure’ by the way).
I didn’t read through everything so apologies if this is repeated information, but it may contribute to your problem if you did not harden your plates thoroughly enough after drying thoroughly enough. Your plates probably need about 3 times the amount of time they were in the water at about 125-150 degrees F depending on what the manufacturer recommends, and please understand this is a guess. So, gentle heat for a long period basically, to force the water out of the polymer and harden it up, and then a post exposure will allow it to reach it’s maximum potential durometer.

Photopolymer is pretty soft until it is completely dried, and then post exposed for the appropriate amount of time. It sounds like it being too wet or under-exposed is the problem, but judging by it ‘sticking to the glass’, I’m going to go with too wet and that you need more drying time.

Don’t worry, once you get a good plate, as long as you record your steps and the amount of time/values for each, you can repeat as necessary to continue making great plates. This has a learning curve but you’ll get there.

This is the info I was referring to re: kreen and shoulder - I would say experiment and see what results you get - best of luck!

You can sandwhitch the kreen between
the glass,and negative. if you don’t use kreen the plate
will have no shoulder. best james

* james bourland
* on 8 Nov 10 (10:32)

Erroneous information.
Kreene, when properly used, is applied as the only thing between the polymer and light. It’s suctioned down with a vacuum base or some hoses of some type depending upon the setup, and is what maintains contact between the negative/film and the polymer being exposed.

In non technical terms- the thing that determines shoulder is the undercutting angle of the cross light which occurs due to the kind of lamps used to expose polymer. Tubes, not bulbs, are preferred, and are arranged in a linear fashion with even spacing and at a flat distance from the polymer itself of only a couple inches. The light floods and radiates out omnidirectional, and so it creates angles. Undercutting.

To quote a guy I know who knows a lot about this sort of thing, “Draw a line and then draw a point over the centre of the line. Now draw rays from the point to the line. In the centre, the light hits straight on and is the strongest (shortest distance for the UV rays), and this would give you a sharp edge on your stencil. Out by the edges, the light hits at an angle, and depending on this angle, it undercuts the stencil edge.”

The distance of the light source from the polymer is what determines the angle, and the amount of radiation/time the polymer spends under the ‘light’ is what determines the width or spread. More light or closer, a mellower/wider shoulder more like a rolling hill. Less light or further away, a harsher/narrower shoulder more like a mesa.

The trick to having a good exposure system for polymer is striking a balance between the amount of UV radiation the polymer receives and the distance to the lamps; it would seem, in my practical experience, to have very little to do with introducing kreene into an exposure unit to diffuse the light.

just wanted to suggest/double check the exposure unit was made for polymer plates, not stamp making/other purposes, as polymer needs certain spectrum wavelengths of light, check lamp wattage is sufficient> Gerald Lange Bieler Press publishes a super book I recommend purchasing on plate making, check out his polymer website/forum too,re advice that fonts etc must be suitable for polymer. not necessarily will anything work from an Illustrator/Indesign font, generally the recommendation is that finer the font the thinner the plate must be, eg .43- .73 steel backed for fine fonts/style of type.
MacDermid website has many technical sheets on view/for download re testing for correct exposures for polymer plates, always assuming the negative is opaque enough of course

bebbachan

I’ve been watching this for a while now but had no rationale way to contribute. Re-inventing the process just does not seem feasible with what you have, knowledge, equipment, etc.

You would save a GREAT deal of time and energy, and money, just by buying your processed plates from Boxcar or Elum.

You want to print well, right? Buy the right tools and materials to do that.

Gerald
http://BielerPress.blogspot.com

Hi everyone,

Thank you for taking the time to help me out.

Gerald, it is too expensive for me to buy plates from elum and boxcar along with the postage. I switched from plastic photopolymer plates to metal backed and everything is working now.

My UV exposure unit is suitable for making photopolymer plates.

Thank you again everyone. I appreciate it :)

bebbachan

Congratulations in solving the problem.

Interesting, actually. I only work with Toyobo brand plates and find the steel-backed and polyester-backed 95 mm plates (rated the same hardness) to be identical in processing.

But going to the 152 mm plates there is a significant difference. The polyester-backed plates, rated softer, are quite problematic. No such problem with the steel-backed.

Any difference in the hardness rating of the plates you were, or are now using?

Gerald
http://BielerPress.blogspot.com

I tried some sample harder plates too recently normally d73s but these were m73 something Miraclon, needed higher temp and bit longer exp and wash out, is it just a higher concentration density of polymer I wonder that makes them harder, or other components……………..hhhmm

Hi all,
i’m a newbie here…I have exposed the plate for 2 mins with my 32W uv exposure unit and went for washing using warm water. The image is there but seems that there is no difference to the thickness creating the depthness. Can help and advice me? Thanks a million…

image: IMG_1972.JPG

IMG_1972.JPG

image: IMG_1970.JPG

IMG_1970.JPG

image: IMG_1968.JPG

IMG_1968.JPG

I’m supposing the exposure isn’t long enough.

But the only time I’ve ever seen something like this was when a student exposed a plate with the protective polyester film coating inadvertently left on. Even with the exposure correct, washout did her no good.

Gerald

sounds likely Gerald-poster does not mention how plate was washed out —by machine or by hand??, with still bath then a soft brush like the ‘solar intaglio” or with a proper/ bristle type brush by hand…..

Hi all masters, what’s the recommended exposure duration? My uv exposure unit is 4 X 8w tubes.

I did peeled off the protective polyester film before exposure. I tried making the plates (2 separate plates)…one by transparency film and the other by black negative film. The image with black negative film is slightly deeper but not so clear. The image with transparency film is clearer but not so deep.

Attached picture…left is the black negative film, right is transparency film.

image: IMG_2002.JPG

IMG_2002.JPG

image: IMG_1997.JPG

IMG_1997.JPG

Richard

You are not providing the technical information needed for anyone to actually help you with this.

To get proper exposure all you have to do is find the specs for the plate (a thick Jet?) and, based on the target exposure for the plate, run gray scale tests until all is well. It’s quite simple actually.

I’d bet if you had just sent the e-file to Boxcar or Elum, you’d have saved a lot of time and money and the piece would be printed by now.

Not trying to be nasty, just commonsensical.

Gerald

Hi Gerald, the plate supplier told me he don’t know the specs and told me to expose it at 1 min which I tried and failed again. I believe the negative film is dark enough. Uv machine at 32w not powerful enough?

You mean email the artwork to Boxcar and after the plate is done, ship to me in Singapore? How much will that be? I’m just trying to get some knowledge and advices, learn how to do it rather than always depend on outsourcing.

on my plate making machine for a plate 35 x 55 cms =8 x 40w lamps/tubes

macDermid on their www have technical sheets to look at /download to test correct exposures.

that gives me an exposure time of 2 minutes for a Miraclon d73s plate, slightly shorter time for b94f

Richard

Well, if you live in Singapore, nope. But if you are buying plates there certainly must be a processor around there somewhere.

Who is the manufacturer/what is the brand of your platemaking machine? Is that black negative film silver-based? And what is the manufacturer/brand of the plate?

Everything would be soooo much easier for those trying to help you out if you would just provide the information to allow us to do so.

Gerald

If the negative film worked in blocking the exposure of the non-image areas, but wasn’t clear enough in the image areas to allow good exposure, you may need to modify the exposure or development of the negative to keep the image clear. The other film you depict seems to have much lower density than is required. When using a “thin” negative like this, the light passes through the film enough to start the exposure of the background, and washout becomes extremely difficult or impossible.

John Henry

How close were the lights to plate? They should be very close - think 2-3 inches. Also, sometimes it takes a minute or two for the photopolymer to really start moving. Make the water as warm as you’d like your shower and keep it flowing over the plate. You must also use a proper photopolymer brush - something soft, but well bristled. Perhaps a soft toothbrush type texture.

You’d be surprised how dark the negative needs to be. Try a step exposure (just look up how to do one, it would take me forever to type), basically expose the same image at different times on the same plate and wash out to see how much time you need. On one jerryrig exposure unit we needed to expose for 6 minutes!

Oh, also. Once I accidentally exposed a plate with the protective film and it still washed out just perfect. I was pretty surprised, myself.

@bebbachan, perseverance always pays off. I too, use the steel backed plates.
@ HavenPress, It might behoove you to read a thread before you debunk it. I read your post from jan 6 and the
1st pargraph is a contradiction.
best james

James,

In the spirit of understanding, perhaps you could point me towards this contradiction?

-Mark

I’ve got both a point light source and a polymer processing unit. My comments weren’t meant to debunk so much as provide insight into my experiences with working on polymer plates.

I’ve tried both, and I wanted to post an example of what a vac base with kreene looks like and what a point-light source with a glass contact frame looks like.

Kreene, suctioned down over a neg, on the vac base of an A&V platemaker. Notice the KREENE is what is suctioned down:
http://farm9.staticflickr.com/8237/8445993554_a686b243ea_z.jpg

The platemaker with the kreene peeled back, displaying the vac holes and air-channel grid:
http://farm9.staticflickr.com/8076/8444913705_b9a8f2c510_z.jpg

Now the Theimer point-light source litho plate exposure unit I have:
http://farm9.staticflickr.com/8214/8444909519_9e05391f3e_z.jpg

Note the single hanging bulb. This is not any good for polymer because all the light comes from one source, and is diffuse and even in radiation; so it doesn’t undercut and make a stencil that has any kind of shoulder.

Open, detail of the vac blanket and hose apparatus- that little brass thing is what suctions the air out and pulls the vacuum against the BACK of the plate, rather than pulling kreene down on the FRONT of the plate:

http://farm9.staticflickr.com/8092/8446006560_d06eff89e8_z.jpg

~~

FWIW, I have put kreene into this unit on top of polymer and exposed to a solid with a stouffer scale, then repeated exposure through an imagesetter neg, and it doesn’t really work as well as the polymer processing unit with it’s bank of tube lights.

My personal experience with these two units and the results is what leads me to comment about Kreene. It may well work for others and I have no way to know about it.

Mark, First sentence states kreene as the only thing between the polymer and light. Second sentence introduces negative/film. james

Oiy vey James. Kreene, Neg, Plate, Base. Add vacuum. Sorry for the typo/confusion. Process and explanation.

Mark I also use both units, as well as the sun. The commercial plate maker needs a bulb with the correct spectum for photopolymer. I too base my advice on experience, when I expose with the sun and electric
point light sources I sandwich krene, neg/pos, polymer
and I get shoulder. Without krene, straight dropoff just
like the white cliffs of Dover. best james