From Inkjet Art
In recent weeks there has been considerable discussion about out-gassing "fog" appearing on the backside of the glass in framed Epson Premium Luster prints, printed with the new Epson UltraChrome inks. It has been suggested by some that this situation could equal Epson's problems in the summer of 2000 that were experienced with the dreaded "orange shift" fading with the Epson 1270 inks on the Epson Premium Glossy Photo Paper -- where Epson initiated a printer and media buy-back program to save face (before reformulating the paper that fall with anti-oxidants to slow down ozone oxidation of the cyan dye).
Before I go any further, let me assure everyone that the "out-gassing fog" coming from Epson's Premium Luster and UltraChrome ink is NOT an Epson-specific problem, nor is it an Epson UltraChrome ink problem. It is a PAPER-SPECIFIC PROBLEM. This is a problem that is specific to a type of paper, mainly "RC" or barrier type photo inkjet papers. The problem is not specific to Epson brand "RC" papers --there are many other brands that share these specifications. The problem is not even limited to our industry.
The out-gassing fog comes from the glycol, a wetting agent that is used in all inkjet inks. "RC" photo inkjet papers have a barrier layer (usually polyethylene) between the inkjet receptive coating and the paper base. This barrier prevents heavy ink loads from wicking into the paper (lowering image resolution, contrast and color saturation) and from moisture that causes paper "cockling" (deforming wrinkles). However, this same barrier can prevent the ink from drying quickly. Although the paper may appear to be dry (and is dry to the touch, especially "fast-drying" micro-porous papers like Epson's "Premium" line), there is still plenty of water and glycol under that super-absorbent coating, lying against the barrier layer.
It is this water and glycol, trapped against the barrier layer, that may eventually out-gas (evaporate) and condensate (fog) on the inside of the glass, if a print is framed before it has had a chance to sufficiently dry. Some have noticed that the fog on the glass is "oily" to the touch. This is from the glycol.
People in the inkjet signage industry have long ago noticed that they must let their RC type photo papers dry for several days before they can thermal laminate these papers -- otherwise the trapped water and glycol will immediately turn to steam and create bubbles between the laminate and the paper. Some RC papers never dry quick enough (who can wait two weeks?) to laminate.
A spokesman from a third-party inkjet ink company recently told me that it was once necessary for them to change their glycol ratio in the inks used in HP printers, otherwise their inks never did seem to dry a host of media types.
Epson's new pigmented UltraChrome inks (and any of their other inksets) have no glycol drying issues on matte and fine art papers. There are also no drying problems (that we know of) with their cast coated glossy photo papers, i.e. the Epson Photo Paper (now called "Glossy Photo Paper") and their Glossy Paper Photo Weight (also called "Professional Glossy Paper" in the sheet size).
Accelerated drying procedures may be needed when framing Epson "Premium" papers (and all other RC type papers) behind glass to avoid out-gassing fog on the glass. Epson and other companies suggest waiting at least two weeks before framing barrier type photo inkjet papers behind glass. Epson's Greg McCoy has another suggestion for those needing a quicker solution:
"The process needs to be accelerated, and by 'curing' the print with a plain piece of paper in contact with the print for 24 hours.
"After 24 hrs, you will notice the plain sheet of paper is wavy.
"On a print with heavy ink duty, I recommend changing the paper after 24 hrs and a new sheet and let it sit another 24 hrs.
"This is necessary for any print on a barrier paper that will be framed under glass or placed in a plastic sleeve."
I hope Greg's suggestions will help. Although this procedure is somewhat of a production 'pain', it does offer a solution to those who can't wait a couple of weeks to frame their prints. Undoubtedly, some industrious person will invent a heater/dryer unit for the inkjet industry similar to what they've done in the litho printing industry to solve their out-gassing problem on prints that have to be quickly framed for the art shows.