An offset printing quality standards checklist is essential for any pressroom. Without it, pressmen will make their own judgements as to what is acceptable and what is not. If management is serious about quality, they will effectively communicate well defined parameters of all the pressroom variables that effect quality.
Making a checklist is not rocket science but sometimes you just need somewhere to get started. Here is an outline that will help you get started.
1. Finishing Standards
Whether it's sheetfed offset printing or heatset web offset, paper will wander as it travels through the press. There are of course many controls within the press right from the pile of sheets or the flying paster to keep it aligned. However an exact measurement as to how much wander is acceptable is necessary. If the copy is folded or trimmed, how much is it allowed to be out of alignment before it is unacceptable? These things must be clearly spelled out.
2. Ink Standards
Unless you are running the ISO standard and measure your color in Lab values, having a standard on ink densities should suffices. Define what the standard is and how much variance is tolerable. Inevitably though, you will need to make judgement calls on what color is acceptable and not. Establish a procedure for making those calls - who is called and at what point.
Unless you're a hacker, no scumming should be acceptable. However I'll admit, just like any other pressman, that some light yellow scumming which is barely perceptible gets through sometimes. If you print daily newspapers, perhaps a little worse is acceptable. This needs to be defined by management.
3. Hickeys and Other Defects
Hickeys are a fact of life with printing. If its on the front cover on someones face, it obviously needs to be taken care of asap. If it's on a picture of a starry sky and blends in with all the others, it's not so bad. Clearly define where a hickey is acceptable and unacceptable or how big it is before it becomes unacceptable.
I'm sure that everyone has seen that daily newspaper that you could hardly understand what the pictures were because the register was so far off. Detailing exactly how much register is allowed to be out of alignment may prevent copies like that from getting out. Granted, if a press does not have automatic registration, it may take longer, but it shouldn't change when the press operator starts saving copies.
5. Plate Problems
Scratches happen on plates which causes a sensitized are of the plate to be shown. When it does happen, at what point must the press be stopped to fix it? Sometimes plates will crack causing a line to show. This must be defined as well.
6. Dot Gain
Whether it's ink and water balance or just plain plate wear, dot gain variations occur throughout the length of a print run. If color is critical, you will want to monitor it and decide how much or lack thereof is acceptable. This should especially be on your checklist if you aspire to the ISO standard.
Other Quality Issues
There are a myriad of other printing defects that can occur and these must all be defined in a checklist that is visible to the press operator. Particularly, it should be put at the place where copies are inspected and passed for acceptability.
Perfection should always be the goal for any good pressman. However for those times when a judgement call must be made, don't leave it up to the judgement of the pressman. Tell him what is and is not acceptable.