“Gas ghosting, also known as gloss ghosting, is the transfer of a printed image from the front of one sheet to the back of another. The transfer is caused by a chemical reaction when vapors from ink drying on one side of the press sheet interacts chemically with dry ink or paper coating on the other side of the sheet. Gas ghosting can also result when the ink drying on the second side is accelerated or retarded by fumes given off by ink on the first side. The problem is typically solved by changing the chemical properties of one of the variables in the process.”
I recently experienced this ghosting at work. Here are the specs:
Final size 8"x8" booklet cover
Printed two out
Sheet size 20"x28"
100# Productolith Dull Cover
Work and Turn
PMS 877 [Silver], PMS 295 [Dark Blue], flood dull varnish
Printed on Heidelberg SORZ
Wet trapped
The photo shows the gas ghosting of the lion shrine statue [it appears almost like a negative on the solid dark blue area]. It showed up predominantly only one side of the printed sheet. Next year, we plan on printing PMS 877 silver first, let it dry a few days, then come back with PMS 295 [dry trapping]; after that dries, run the varnish. This would be a very cool technique to do on purpose; I wonder if anyone has created a gas ghost intentionally on a printed piece?
More on ghosting can be found on Gordon Pritchard’s blog, “Quality in Print,” here and here.
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