Spray powder effects on offline UV coating

[aqazi81]

What kind of issues we can get in offline UV coating if a job printed with conventional inks and anti set-off powder was used?

 

[Cornishpastythighs]

Here are a few I can think of if excess powder is used and I'm sure there are many others.

Sheet will have a rough 'sandpaper' feel to it
Uneven gloss with dull and glossy areas.
Piling on the plate/blanket
Spray residue in the equipment.
Slip would be poor if you are putting product through other equipment like a folder/gluer

I also believe that for UV coating to work well over Conventional ink you had to apply a Primer coating first

 

[Seeking Knowledge]

Hello,

When powder is used, it needs to be removed before UV coating. 2 ways to accomplish this, that I am aware of, running it back through the press with the Powdered side of the sheet touching the impression cylinder. The other is if the UV coater has a crusher unit installed.

If there is powder on the sheet when coating you will not like the results, it will look just like Mr. Pasty Thighs said. I will add that there will be voids in the clear and it will not have that nice smooth finish.

SK

 

[aqazi81]

Thank you all for your input.

Another question, can coated or uncoated spray powder make any difference in UV coating or both types can cause similar issues?

 

[Cornishpastythighs]

Aqazi81, If you are encountering an excess of anti setoff spray issue often we found these lamps helpful to detect too much offset spray on the sheet. We run 44" and 50" presses 6 colours plus coater and run high ink coverage jobs for packaging. Every now and then no matter how good your spray unit you could encounter a 'Spray Bomb' Good luck
https://doylesystems.com/landsco-lights/

 

[aqazi81]

Here in our country the offline coating units are mostly made of an old press and aftermarket UV driers. The UV coating is transferred through ink fountain to rollers, plate,blanket to substrate .
​​​​​​So as alibryan said, the roller coaters apply higher amount of coating layer to the substrate, this prevents issues related to powder. On the other hand the method that I'm referring to is always prone to these issues.
The spray powder build up on blankets during coating and cause uneven coating and sand paper feel to the finished product.