G7 curves using Specta screening

[RGPW17100]

About a year ago we had a G7 master come to our facility to do the certification process. I am a press operator so I dont want to get too technical so here is my issue. About two months ago our main press operator left (SM52 2006 with pre inking software) and did the re certification for our G7. After he left we have been having a lot of problems hitting proofs. Normal densities that have given us the lowest delta E are C=1.38, M=1.41, Y= 1.03 and K=1.75 (coated inks with gloss aqueous on flo gloss paper). In order to match proofs I have to run K at 1.50, C,M and Y at 15 points under density. Also my prepress tells me that the same curve is applied to all three matte, gloss and uncoated. I am almost positive at the place I worked at before there had to be different curves for each different stock. We are going to run a G7 target tomorrow to try and find where we went bad. Is specta and pretty reliable and predictable dot to use? Also we are using Fuji thermal plates. Sorry cant remember the exact kind of thermal they are.

 

[Kaoticor]

You are correct, there should be different curves applied to different paper stocks. You have to hit different numbers for different paper types, so that is kind of a big thing! If you are using the same curve which is targeting an uncoated paper for a gloss paper, you are going to notice a significant difference... I dont know why that would suddenly change when your lead operator left, but would definitely give you the problems you are describing.

- If you are using a curve made for an uncoated paper on that gloss run, that would cause you to have to run everything lower to try and match the targets.

K