EEM/EAM Deacidification -- Wei To spray #12
2003-02-17 by Paul Roark
Short version: The Wei To #12 spray, in initial tests, deacidified the EAM/EEM sample through the entire paper base. The sprayed sample is now "acid-free." The long version: My favorite paper continues to be EAM/EEM -- if it were only really archival. Unfortunately, it is not because it is acidic. It is made of un-buffered wood pulp, which, unlike cotton, has lignin in it that turns acidic when it is broken down through oxidation. Unfortunately, while the lignin content of EAM/EEM appears to be very low, it is apparently impossible to totally remove it from wood-based papers. The acidity will eventually attack the cellulose and destroy the paper, but this will take many years. Epson and others have said that the acidity is also what causes the paper to turn yellow after a number of years (30 - 65 seems to be the range). Lignin by itself, even if buffered, is photo-sensitive and will yellow with UV exposure. I have put test strips right next to a UV lamp for 100 hours and observed no yellowing in EAM. An informal, preliminary test by a person in the preservation industry also saw no signs of lignin. Buffered wood-based papers can be archival. The buffering simply mops up the acid's H+ ions before they can do any harm. If there were no acidity in EAM/EEM, it might be quite archival. I use an Abbey test pen to test for acid. When it hits acid it turns yellow. When there is no acid (H+ ions), it turns purple. The untreated EAM/EEM paper base turns yellow. Even cheap, wood-based paper is often buffered and turns the test pen mark purple. Buffering is cheap, so it is a little surprising that Epson did not buffer EAM. On the other hand, Epson may have chosen not to buffer EAM/EEM for some very good reasons. One article I read indicated that a better gamut can be achieved if there is no buffering. EAM/EEM's relatively good dmax, light-fastness, non-flaking, smoothness, or other performance characteristic might relate to the acidity or lack of buffering. I have no idea what was behind Epson's decision not to buffer the EAM/EEM paper base. There is a small "deacidification" industry that caters to libraries and other conservation and preservation-oriented organizations. Claims of 300% longer life for acidic paper documents and artwork are often tossed about. My thought is to simply buffer the EAM/EEM prints after printing. If a spray on the back causes the paper to test as non-acidic, and it stays that way for a reasonable time, we might have the superior performance of the un-buffered paper with a life-span that is very long indeed. In fact, if the print is not dry-mounted or coated on the back, it could be re-buffered if it ever tested as acidic many years down the road. I have tried the Preservation Technologies spray. It deposits a buffer on the back of the print. Unfortunately, the buffer does not penetrate the paper. As such, the back tests as non-acidic, but when ripped open, the interior fibers still show yellow with my Abbey test pen. I just tried the Wei To spray -- #12. It appears to soak into the paper. One slow sweep of the spray across the back is enough so that the interior fibers are testing non-acidic throughout the paper. In the past, I've been able to de-acidify EAM with ammonia. However, the gas leaves no buffer. So, those samples turned acidic again in a matter of days. The Wei To leaves a buffer that should keep mopping up the H+ ions for some time. The question of how long and how much buffer is needed in the interior for a reasonably long life is unknown. I'll be testing the sprayed samples and exploring that issue (among others) in coming weeks/months. The company probably has some information that will help. I think the potential user base here is large enough for the company to pay some attention to the issue. Acid-free (cheap) EAM/EEM -- it's worth pursuing. Paul http://www.PaulRoark.com