In order to achieve the difference in the paper, the water drawn from the river Erme in future was to be filtered to achieve continuity and quality control, as it was believed that this would reduce the colouration in the water which previously had a tendency to fluctuate especially with heavy rains, this would rectify the slight colour changes that had been currently found in the cream manufactured stamp paper.
An article on the subject was composed by the late professor Austin J Barnes and published in the British philatelic journal in 2020 Vol 58 no.3 on pages 68/69, it can be read as follows >
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In total over the years I have discovered that between 1958 to 1967 a total of 5 different base papers have been used to print the multiple crown Wilding stamps, I have made up a list of the different ones that can be found with the use of a long wave ultraviolet light.
Of the five different papers used to print the Wilding stamps that I have found, the first two papers are well-known examples and have been identified and currently listed in the Stanley Gibbons part 3 specialised catalogue, here are the five variations which I think are in chronological order in respect as to when they were produced either by error or design.
(1) The original cream type paper which was produced up to 1962 was replaced after a statement made by the GPO of that year, this is listed as a paper variety in various GB specialised catalogues.
(2) A whiter paper variety that replaced the original creams, supposedly created to enhance the capabilities of the ALF system, this paper was supposably made by filtering the water which was drawn from the local river, this paper is also listed in specialised catalogues.
(3) A paper that appears to be encrusted with fluorescent fibres/particles in its embodiment as seen on various denominations, especially of the 9½mm violet phosphor definitives printed on a whiter paper, caused by the use of rags containing high amounts of stilbene dyes used in the production of various washing detergents, this type of contamination was first seen around 1964 and gradually increased as time went by, many values have been affected including some commemoratives, add to the fact that there could have been a possible change of rag supplier around that time.
(4) A cream type paper similar to the original 1962 creams but of a more translucent nature discovered on much later printings, this type of paper was in my estimation created by the use of chemical degradation to rid the paper of contamination using substances such as chlorine dioxide or ozone, a method known as oxidation, however, this left a residual paper totally lacking in fluorescence as against the intended whiter paper required.
(5) A fluorescent paper that was created with the additional use of optical brightening agents (OBA's) whilst the paper was still in the pulp stage, used in order to camouflage/mask the offending contaminants, good examples have been found of the 10d 9½mm violet phosphors, other values printed on this type of paper are also known but are not as numerous as the contaminated ones that range from the 1d to the 1/6d with a few exceptions.
I will endeavour to show you examples of the three types of paper 3,4 and 5 that are not listed in specialised catalogues , these will cover normal definitives, regionals and some commemoratives to a varying degree.