Does anyone out there know of any means to calculate the percentage of moisture that is added to a sheet of paper whilst running through a 4 colour press. I know this depends on how high your damping is cranked up but is there a set equation to determine the amount of water that the sheet absorbs? The reason I ask is that I am trying to balance the RH of the sheet to the RH of the room as I work in a very dry climate that causes major issues with stock even after it is acclimatized. Thanks in advance.
You know there are alots of varibles in that question, type of paper, how well the damps are set, how the air flow in the building that is heated, does the operator run the press, is there a shipping door in the room that allows outside air in, are just a few off the top. In the winter months the 8c has a greater chance of creasing because of the lack of RH, and the size of the room makes it hard to control, and the shipping doors that open and close all day makes its harder yet, but I would say a easy 6% to 10% with one of the guys for he always runs the water high, where myself I run a finer setting and I get way less creasing because I feel that less water makes for a sharper print, will watch that in the days to come, good post. FSA
You can buy a moisture reader, that's what we have in our shop. We adjust according to the reading to create a consistent end moisture content. As far as a means to calculate, not sure. K
I suspect you are having trouble feeding stock and perhaps even registering, either front to back or color to color on seperate runs. I have eliminated most moisture problems down to the paper stock itself. I tend to order stock and have a supply in the shop , for several days prior to run. this will pre-condition the paper to room conditions and I have less moisture problems. running stock shortly after it comes in off the delivery truck really creates more issues, especially in the winter months.
As per the paper manufacturer, the RH of most of their products fall within the 45% +- 5-10%. The RH in my shop is around 20% on a good day. I understand all the factors concerning the conditions of the environment/press etc. Paper will acclimatize to the TEMP but not necessarily the RH if its wrapped/boxed correctly. I have humidifiers blasting all day every day to get as close to equilibrium as I can. I suppose it is what it is and my issues (mainly registration) seem to be common wherever you are and we just have to do the best we can or go insane! Hopefully more people will comment on this post as its becoming quite an interesting topic. Thanks.
