In 1987 the USPS introduced a new (to us) tagging method, prephosphored paper. Essentially all stamps this year were Block over Vignette tagged, except for two notable issues, phosphor-coated paper test stamp (discussed in next paragraph) and the Drafting the Constitution booklet. On this booklet, the USPS elected to use a phosphored band over the vignette - a continuous horizontal wide band over the stamp design. The band misses top and bottom perforation areas of each design (left and right perf margins tagged). BEP also used a new water-based ink to improve printing brilliance; however, the taggant-lacquer coating applied to this issue cut down the brilliance. On future tagged stamps without lacquer-coated overprint, the new ink should be apparent. Future tagged stamps without lacquer-coated overprint? Yes, it's on the paper.
As previously mentioned, taggant placed on top of printed stamps has several disadvantages - reduced brightness, corroding perf pins and cutting knives as well as cancellation problems. As mentioned in Linn's Yearbook for this stamp, we are not the first country to use prephosphored paper - the Netherlands first used a similar technique back in 1962. Also Linn's stated that the zinc orthosilicate treated paper has a weaker taggant formula than the liquid phosphor/varnish used on press. The prephosphored paper has its taggant phosphor over the entire sheet and not placed just over the vignette area. So, wear on perf pins and cutting knives will still be present (but reduced).
TOP: TEST COIL WITH PREPHOSPHORED PAPER
BOT: PRESS TAGGED BLOCK OVER VIGNETTE
As seen in the above picture, prephosphored paper show no tagging pattern whereas Block over Vignette tagging is obvious under short-wavelength UV light. The prephosphored paper eliminates the need for tagging rollers (no press slow down), does not degrade ink brightness or cancellation ink's inability to penetrate into the paper. However, wear and tear on perf pins and cutting knives still exists and this is what the test is designed to focus on. With this stamp and the 1988 Official Mail stamps, the phosphor was added as a coating after the paper's manufacture. For the next generation, the paper was treated with phosphor with large cost savings. You mean there's more than one type of prephosphor paper?Yes.
In 1989, the USPS issued the first full-production stamp on pre-phosphored paper - a reissue of the 1988 25 cent Flag over Yosemite. However, a different approach was used to prephosphor the paper - the paper was treated vice coated. Under short wavelength UV light, the difference is readily apparent. The coated paper is smooth and consistent whereas the treated paper is blotchy and speckled as if lightly sprayed on and does not cover the entire surface; the original unphosphored paper is visible in the background. The USPS states that the treated paper costs about half that of the coated paper. So .... you know which manufacturing type won out in the battle of the prephosphored papers. Wrong! and wrong again! As demonstrated by Souvenir Pages issued in 1998, we are getting both types even though the latter is cheaper. Normal decision makers making a decision as a group. Without the varnish barrier, cancellation ink penetrates the treated paper better and thus better guards against reuse of "washed" or "cleaned" stamps, the number one crime on the USPS most wanted list which incurs revenue losses of $300,000 a year. Check your Pages on these two issues to see, as claimed by the USPS, ... the whiteness of the paper is more apparent and more vivid colors are achieved. The printed portion of the stamp seems to be raised from the paper to a greater degree than conventionally-printed stamps. In 1987, the Postal Service said it successfully tested the use of pre-phosphored paper to determine its compatibility with mail processing equipment.
The table on the next page summarizes tagging types. The acronyms are mine; also listed are specific Souvenir Pages that corresponds to these tagging types. Two types of tagging listed on the table below need to be discussed in further detail: BCA and OBE. First BCA - where tagging appears in isolated areas (taggant applied in customized cut-away blocks) vice in rectangular blocks. As illustrated by the pane at the right, the Classic Car booklet pane as photographed under UV light, shows the Block Cut-Away tagging as a white background under the car which cuts around the car tires and body of each car type.