over packing and ink coverage

Hi all, working on a job, the client requires a deep impression. ( insert rant ) (/end rant)

I am using a CP 10x15, I have the deep relief boxcar base but use regular relief plates ( adhesive photopolymer ).

I the image area on the bottom of the platen ( towards the floor ) is significantly darker than the top.

The platen is level.

Is there more pressure on the bottom because it closes there first and this is magnified by the over packing?
I am using card stock under book board for the packing.

Could it be a result of the deep relief base / regular relief plate ?

I did search the forum, just wondering if anyone has experienced anything similar before I start mucking about.


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If you have heavy impression at the base of the platen then you are over packed and need to adjust your platen accordingly after removing some packing .This is always where heavy impression is a grief as you will find getting the adjustment right fotr a hard material will require a wildly different setting than for a soft fibred stock like cotton even if they measure up to the same thickness .. Its what makes the task of printing clamshell so hard to get used to and why everyone asks what may seem like odd questions when you need help.

Peter is right about the packing part of the problem but the inking part must also be examined. A low relief plate on a deep relief base will be well below type height. Any C&P will probably have tracks that are also worn below type height, but to varying degrees. The common roller gauges are only intended for .918” forms, so using them in a low-plate/low-track situation will be misleading. You need to get control of roller contact to plate. (q.v. a thousand other posts).
Personally, getting plates to .918” and then taking precise control of track and truck height is what works for me.
Note that level of platen only exists for a specific combination of stock, packing and form height. Change any of those variables and the platen is no longer level.


This is a handy guide that explains packing and leveling the platen.

Thank you everyone. I had levelled the platen using the recently mentioned solder trick, prior to that I did it with the capital Ms in the corners.

I usually have 3 - 4 pieces of green painters tape on the rails.

I can print these on my proof press where all this becomes a non issue - it then switches into the issue of making 500 impressions by hand as opposed to my recently motorized CP.

Live and learn, and in between I think I will order the regular relief base