Duplexing curl and show through woes

Hi everyone,

My father and I run a small offset/digital/letterpress shop and just when we start to think we’ve got it all down pat, the universe throws us a monkey wrench.

We’ve been blind embossing a business card logo for a while now on 100lb Mohawk Superfine Smooth, printing the info side on another sheet of Superfine, and mounting the two together with good results. But on the last two print runs we have seen the finished cards curling and the paper “sucking in” to the space of the emboss, leaving a reverse impression on the back side.

We glue using a Potdevin with P200 glue and a brayer to finish. Then we stack and let sit under weights over night. We have tried crossing grains, adding a third sheet in the middle, but we’re not getting back to where it worked. We used to have an old plate processor and we’d put the sheets through the rollers to squeeze them before pressing them. But that finally died and we switched to the brayer, which *seems* to have worked…up until now.

So I’m running out of ideas. Just wondering if anyone has had any experience with these kinds of conundrums and what they have learned on the duplexing front.

Apologies in advance for being a lurker except when I need help! My father is the one who’d really be helpful here, I know enough just to be dangerous. Thanks!

Tony

Log in to reply   7 replies so far

Tony, Two things to consider and try.
If the only apparent change to your process is using the brayer in place of the pressing roller I would eliminate the brayer. Just hand rub the two sheets together and place under weights.
You could be laying down to thick of a glue layer. Bonding of the sheets can be accomplished with a surprisingly thin glue layer although the ‘open’ time will be short.
When duplexing two sheets of the same stock there usually is not a curling problem. That is why I am concerned about the amount of glue. the sheet accepting the glue may be to wet and will curl until the moisture balances out.
let me know your thoughts on these two items. also keep your original run under weights and see if the curl relaxes although that may not help with the sucked emboss. problem.
Call me if you like:)
Jon Drew/Mpls
Duplexing & Beyond
drewpress.blogspot.com
612.270.6449

Hi Jon,

Thanks for the response. Your site is wonderful! Gonna lose myself there for a while, for sure. What a find.

I will definitely check the glue flow and play with that, I didn’t even consider it. So obvious.

Thanks again and I will be in touch!

Tony

Lower humidity in heated winter environments can amplify problems which seem manageable in other seasons. Make certain that both sheets being laminated have had the same exposure to the environment in which you are working. If one comes out of storage are and the other has been in a different environment, that can give you differing starting internal humidity, and cause curling. Also if one is exposed to the adhesive longer before laminating, that can be a problems. too.

John Henry

Are you stacking them in a perfect stack, all facing same direction?

My thinking is that if the glue is too thick (as 2001fred brought up), and the raised portion of the emboss is directly beneath the cavity of the next piece on top…
It could be possible there is a little dimpling effect going on, where the raised portion of the emboss is pushing the paper above it UP ever so slightly, sort of pitching a tent with the emboss high spot…..?

I’m not totally sure of a fix, but if that is indeed the cause you could possibly work around it by alternating and stacking with a blank in between- or some other way to install a spacer that creates a bit of cushion around the raised portion.

Additionally- are these going under a cutter post-glue? (During the cutting might there be a bit of an issue from the clamp? Or are you die-cutting them?)

Happy to report that we adjusted our glue flow and that took care of 99% of it! We bought a cold laminating press and use it to do the final squeeze. Cheap but it does the job.

The paper we have used is always 100# Mohawk Superfine cover from the same carton in the same environment, and the time between applying the glue and mounting is almost nil. Most of our paper is in our inventory for a while before we get to press.

We have been stacking them with a blank in between, since the first run. We’ll see if this final cut makes the impression or not. But we’re going to start using a die cut. It’s too nerve wracking putting them under the cutter!

:)

I’ll keep you all posted on the final results. Thanks again everyone!

Hi - Just curious. Do you laminate them with the grain in the same direction or cross grained?

i have found water based glues will tend to curl a bond, cross grain or not. for small jobs i have found 3M “super 77” or this type of adhesive will not penetrate as much. the sheets stay flat. cross grain mounting is a must. only an amazingly light spray coat is needed