More wavy paper problems to solve

[Tradidi]

After my experience with my laser printer causing the paper to come out like crinkle cut chips, I managed to squeeze the budget and purchase an ex-lease inkjet production printer. (ComColor 7150) I'm happy with the result and even though the quality of the print could be better, I believe it is acceptable for printing perfect bound books, mostly text only.

I also found a good and helpful paper supplier, got some samples and decided to go with what's called Wheki Book stock, aka Holmen. The rep tells me they supply this to most book printers in NZ. I like the color and texture and I would prefer to make this paper work rather than shop around for another paper.

However, I'm now finding that this paper doesn't like our climate and goes wavy after sitting in the workshop overnight. The RH is between 50 and 65%. If I print and bind the books immediately after opening a fresh packet of paper, they look all nice and straight. But when I take them home and leave them sitting overnight, they start waving as well.

I read on this forum about this printer in Israel who occasionally had a similar problem and found that the solution was to let the books sit for two weeks and they would straighten out again.

Question: is the paper the culprit, and should I be looking for a different paper that can handle RH fluctuations and a humid climate better? Or is this normal and should I just get used to letting the books sit for a few weeks before moving them on? If other printers use this paper as well, I would think that they too have these problems, at least when their books leave the climate controlled environment of their print shop? Or am I missing something?

Here's a picture of what they look like after one night:

 

[TJPrinter]

There really isn’t any heat involved with your printing process now but as soon as you open a ream of paper it’s going to react to the changing environment. I don’t see much curl in what you’ve done so unless you can control your indoor humidity you may have to settle for letting the sheets sit for a bit. Perhaps you’re in a coastal region with higher humidity levels but 65% RH would be a problem for me. I try to keep humidity below 55% and ideally under 50%.

Looks like you accomplished a lot to eliminate the curl you started with, nice job!

 

[Tradidi]

Yes, I'm in a coastal region and it can get quite humid here (New Zealand), especially this time of the year.

But the part I don't yet understand is that, even if I can control my indoor humidity to 50% max, the paper will start waving as soon as the finished books leave the print shop. Correct? So then there is no point in spending big bucks installing climate control in my print shop, if all it does is delay the issue.

This must be a problem for other printers as well, no matter how controlled their work environment is. Perhaps I'm too critical in trying to achieve the impossible, but it would help to know that it's a problem that even the big boys can't avoid.. or how they minimise it or just learn to live with it.

 

[SteveSuffRIT]

Try to keep the paper grain direction parallel with the backbone or spine.
Saddle stitched should be fine because paper is somewhat free to move a little.
Hotmelt perfect bound is "locked" in.