I think this is a sufficiently important point to start a new thread.
In a letter from Alec Voller to Nick Warren dated 21 November 1994, Voller says this (with my bold):
"Your question about fading is a difficult one to answer. All aniline dystuffs have poor lightfastness and Nigrosine is among the poorest. But lightfastness is only a factor which comes into play when the writing is actually exposed to light. No ink is going to fade in the pages of a closed book."
Now, we need to bear in mind that when Voller examined the Diary in October 1995 the only provenance story in play in respect of the Diary being a genuine item was that it had been handed to Mike by Tony Devereux (quite possibly having been given to him by Anne, having been in her family since the 1950s). As such, the assumption would have been that, if not a modern forgery, it had probably been opened and exposed to light a fair bit.
But, of course, what we are now being asked to believe by the Diary Defenders is that the book had lain closed beneath floorboards (possibly in a biscuit tin) for many years, perhaps 100 years, before being removed on 9th May 1992. If that is the case then, on Voller's own account, we either shouldn't observe any fading or the fading seen by Voller in 1995 had occurred since the removal of the Diary since 1992. Given the similar fading observed by Voller in 2001 in respect of Nick Warren's test handwriting sample copied at some point between 1998 and 2001, the latter seems to be quite likely.
I'm not sure how this helps to determine whether the diary was under the floorboards waiting to be released into the sunlight on the morning of March 9th 1992, or it had yet to be written on March 9th 1992.
If we are meant to believe the ink was not applied to the paper until the beginning of April 1992, 12 days before Mike took his baby to "that London", are we back to Anne and the completed diary basking under a sunlamp for the final 7 days, so when Voller examined it three and a half years later he would see the equivalent of 90+ years of natural looking, irregular fading?
There must be a reason why Voller thought the diary ink was Nigrosine based [with its poor lightfastness] but not Diamine.
Confused of Sidmouth
__________________ "Comedy is simply a funny way of being serious." Peter Ustinov
The thing is, Voller accepted in 2001 that a document written in 1995 with Diamine ink exhibited similar fading characteristics to the Diary. This means that a document written six years earlier (possibly less if the colour copy that he saw was made earlier than 2001) was, apparently, and amazingly, showing fading consistent with a document supposedly written 80-90 years earlier (or 90+ years earlier depending on which day of the week Voller was speaking). This is before we even need to think about anyone doing something to the Diary with a UV sunlamp. As for the possible use of a sunlamp, Voller expressly said in his letter of 8th Feb 1996 that the use of an accelerated fading apparatus by an amateur, who didn't really know what they were doing, was more likely to fool him than something done by a professional. Thus:
"I also have to say (ruefully) that as a method of forgery, the above technique would probably produce more convincing results in amateurish rather than professional hands because a person unused to the finer points of the operation of the equipment would probably obtain willy-nilly, exactly the sort of uneven fading that is characteristic of old documents."
But truly we don't even need to get to the sunlamp because Nick Warren's sample exhibited similar fading to the Diary which occurred naturally.
As Sam points out, Voller's job was not to date documents. The chances are he was doing so for the first time ever. And doing so on the hoof during a meeting. Moreover Harris, who did know something about dating documents and possessed a collection of old manuscripts, and whose opinion on dating documents has been cited with approval by one of the world's leading experts on the subject, has said that it wasn't even possible for Voller to have dated the Diary in 1995. Thus:
"The truth is that once an iron-gall ink has matured on the paper for eighteen months or so, no one, on this planet, is able to date that ink by visual examination."
By the time Voller looked at the Diary, the ink must have been on the paper for a minimum of 41 months (and just about exactly 41 months if it had been created in April 1992, as the evidence in this case suggests).
In any event, it's odd that the Diary is supposed to show the effects of 80-90 years of fading if it was lying, closed, under the floorboards of Battlecrease when Voller tells us that "No ink is going to fade in the pages of a closed book."