Spot UV BLOBS!

[eyetech]

Hi guys, it's been a while since I've posted but here's an issue that I hope someone somewhere can shed a little light on.

I've attached a pic of an issue that arose when we supplied printed sheets to an outside source for spot UV varnish onto our preprinted sheets.

The image shows what appears to be 'blobs' that turn out to be unkeyed areas of the spot UV. It is contained on one side of the sheet, and runs from grip to back edge.

We printed using our standard ink set + an overall seal water-based coating to both sides of the sheet. We've never had issues of this kind before using our current inks/ sealer combination and the supplier is our regular supplier.

There's only one sheet affected (it's a multipage brochure) and the 'blobs' come and go varying in intensity and location but always in that one 'track' ie the opposing side of the sheet is unaffected as is the reverse.

Any help would be appreciated.

ciao

Richard

 

[Cornishpastythighs]

Please clarify. Spot UV varnish printed in a Litho unit or Spot UV coating printed either by Anilox coater, Roll Coater or Silk Screen. I cannot see the problem that clearly but blobs are usually an indication of some type of leak in a chamber system or build up on the blanket on a roll system and the coating is 'flinging' Certainly worth a visit to your outside supplier for an audit of their process then you will have a better understanding of the issue, plenty of people can do overall UV coating but spot coating requires a little more attention to detail

 

[eyetech]

Hi CPT

Spot UV was applied as an afterprocess on a dedicated Silkscreen UV machine to our pre-printed sheets, (printed using conventional inks and emulsion coated overall). There was at least 48hrs between print and Spot UV application. The blobs are un-keyed to the print ( ie they can be lifted away from the print quite easily ) and vary in size from one sheet to he next as well as in position.

Only one side and one end of the sheet is affected.

thanks for your input if you need any more info then feel free to ask.

 

[GRAPHIC COATINGS]

Are the inks, "STAY OPEN" inks ?

 

[eyetech]

Printed on a Heidy CD 5 colour + anilox end of press coater. Air knives and IR.

It was a 3000 sheet on 170gm silk run so around 45mins …both sides aqueous coated and IR. Then around 48hrs before Spot UV.

Inks are conventional litho veg oil based both they and the coating are what we use all the time.

Open inks - if you mean overnight fresh…i.e. they don't skin over, then yes they are.

There was a separate cover printed on slightly heavier silk 200gm, same amount of ink and spot UV coverage but as it was two up it was turned round (print wise) in half the time. No issue on that or the reverse of the affected sheets.

 

[eyetech]

Update::

Just had the reprint back from the same supplier...same inks, same paper, same coating but this time no 'blobs'