IPA is damaging our coroplast -- printing shows it and it's BAD

[tedbragg]

I've used IPA to get rid of my greasy fingerprints before printing on our UV HP700, but lately everytime I clean coro with IPA it will leave streaks, large swaths of altered surface (flat matte, while rest of the areas are normal) and sometimes it won't even cut the fingerprints off.

I've tried numerous things to correct this, but at a loss. Have they changed the corona coating formula? Our supplier doesn't have any details about this -- Manufacturing is so strained right now, our distributors don't know where anything is coming from.

Tips?

 

[FireSprint.com]

Some ideas:
Try wiping with a solution including 30% water
Try using a Kimberly Clark wypall L30
Try changing the direction of your wiping
Try using more alcohol, like totally saturating your towel
Try a different supplier and/or brand of coro.
Ask for a few sheets from a different batch number.

Of course the best option is to try to buy full skids and not touch the sheet, and if you do, use a nitryle or white polyurethane glove (uline sells them).

When this happens, we set up a file with large 23x47" 50% gray rectangles and start testing 4 ideas at a time. Flip the board over and test another 4 ideas.

Put on your lab coat and start testing variables.

There are no less than 20 extrusion machines/Corona treaters in North America alone. The processes change all the time.

 

[SignMeUpGraphics]

Keep wiping until there is no more IPA left on the sheet. We used to give ours a quick wipe down before print, leaving wet patches on the sheet.
We've changed our methods and will keep wiping until there is no residue left and prints are much better with very little ghosting.

 

[White Haus]

We wipe with 50% water 50% IPA with a fairly wet micro fiber cloth, then buff dry with another clean dry cloth. Long even strokes parallel to the sheet.

Not 100% foolproof but works most of the time. And we only have to do this with sheets that have been handled...otherwise buying coro by the skid usually eliminates the need for this. (No way you're making money printing coro if you're spending a couple minutes prepping each sheet!)

Although buying by the skid isn't foolproof any more, our last one had prints and contamination throughout.

 

[unclebun]

It's probably the excess of hops in the IPA causing the problems.

 

[tedbragg]

I started adding water to our IPA spray bottles and that's helped, but not entirely. Our suppliers (Grimco and GSG) have NO CLUE where their coro comes from, except if its the canadian stuff...

 

[Troy Lesher]

sounds like your IPO having more of an effect on your ink properties rather than your substrate

 

[Inks]

Can you wear gloves when handling the coro? or is it coming with fingerprints? If it is coming with fingerprints ask your supplier to handle it properly and wrap prior to shipping. As far as using another supplier Coroplast, Matraplast and Interplast are all owned by the same company.

Fingerprints use to be a big problem with styrene and OCE printers as they do not lay down a lot of ink. This was solved for the larger printers with the introduction of skid lots of digital grade (never touched by hand). If you are buying a few sheets they are usually off of opened skid lots and may have been handled by hand.