Heidelberg guides help

I’m having trouble registering a sheet today on the press. It’s heavy 200# cover stock. I ran the first pass yesterday and the paper curled a bit overnight. Now, when I run it through, it’s curled so much that it doesn’t catch the left hand side lay. Aside from hand-curling every sheet back to ‘normal’ (it’s over 1,000 sheets), what’s my best option to get this to sit normally? I’m running opaque white on black stock, so it’s requiring a 2nd pass to get the white to be readable.

Here’s an image: http://voteforletterpress.com/heidelberg-registration/

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What’s the pt thickness of the stock you’re printing with?
Type of pulp?
Where’d you get it, and what was the brand?

Colorplan 200# Ebony Black. It’s about 28 pts thick. I just added a second photo to the link above. I manually uncurled a small stack and also moved the side lay further in to the sheet. Now, the initial part of the sheet is in register, but the back part is off by a couple points.

You probably have Temperature changes overnight in your shop, so the sheet sucks up moisture and curls with the grain.

You need to temper your shop.

Yeah, evening out the temperature in the shop would be great, but won’t happen…

I ended up curling stacks of 15-20 at a time to get it back to normal feeding. I moved the lay further back towards the original location and that took care of the registration. Now I have to do it one more time to put the 2nd color on! Yay.

Sounds like curling figured it out.
Question- How did you store your pile overnight?

Because changes in humidity will affect paper, you can shield against this with a bag sometimes. There are times I’ll bag or box the whole job airtight after it is printed, provided it’s small enough, if it’s going to be a significant temp shift (heavier for me in the winter).

But let’s talk about the real problem here, that you’re letter pressing white ink when you should have had it foiled with white foil ;-)

I stored the piles out in the studio, piled high to try to keep most of it from curling. Really didn’t help.

Yes, this probably should have been foiled instead of printed. Oh well. I like a challenge!

I know hindsight is always 20/20, but in future you probably could run the second pass right away instead of waiting overnight. (Or at least you could try that).

That would be roughly equivalent to giving a job two hits in the same run with a hand fed press.

I’m running opaque white on black stock. I’ve found that double-hitting white when wet doesn’t look as good as when waiting for the first pass to dry. It gets very mottled and speckly.