Paper Fluorescence On Modern US Stamps

By Mark Stockburger

Many types of papers have been used in the printing of US stamps. These papers can be identified and classified by their levels of fluorescence and what they look like under Long Wave (LW) UV light. The paper used can vary from issue to issue and within the same issue. Paper can be classified in one of the following seven types.
1. Dead paper (Dead)
2. Non-Fluorescent (NF)
3. Dull Fluorescent (DF)
4. Low Fluorescent (LF)
5. Medium Fluorescent (MF)
6. High Fluorescent (HF)
7. Hi-brite (HB)
For LF, MF and HF paper, the fluorescence viewed is typically produced by very fine thread like fibers embedded in the paper. These fibers termed “luminescent fibers” glow brightly a bluish white when exposed to LW UV light. The concentration of luminescent fibers is what determines if a paper is LF, MF or HF. In all seven fluorescence classification types, luminescent fibers can be present. For Dead, NF and DF the concentration is low enough that the luminescent effect is not visible from a distance. A description of each paper type follows.

Dead Paper

Dead paper appears dark purple, purplish gray, dark brown, dark grey, or dark blue grey under the UV lamp.

Non-Fluorescent Paper (NF)

NF paper appears brown, gray, lighter blue grey or lighter purple. It may contain some very sparse and randomly distributed luminescent fibers.

Dull Fluorescent Paper (DF)

DF paper appears grayish white, light gray, ivory, yellowish ivory, whitish & very light violet. DF paper contain luminescent fibers, which are typically very sparse in density across the entire stamp.

Low Fluorescent Paper (LF)

LF paper appears a dull bluish white, grayish white or white and is not particularly bright when viewed from a distance. Up close under magnification, the paper will be various shades of gray or brown with a low concentration of luminescent fibers evenly distributed across the stamp. The luminescent fibers are responsible for the fluorescence.

Medium Fluorescent Paper (MF)

MF paper appears almost exclusively bluish white and is fairly bright when viewed from a distance. Up close under magnification, the paper will be various shades of gray or brown with a medium concentration of luminescent fibers evenly distributed across the stamp. The luminescent fibers are responsible for the fluorescence.

High Fluorescent Paper (HF)

HF paper appears exclusively bluish white and is bright when viewed from a distance. Up close under magnification, the paper will be various shades of gray or brown with a high concentration of luminescent fibers evenly distributed across the stamp. The luminescent fibers are responsible for the fluorescence.

Hi-Brite Paper (HB)

HB paper is very bright and bluish white in color when viewed from a distance. The fluorescence is uniform in distribution and is not derived solely from the presence of individual luminescence fibers like LF, MF and HF paper. It is very distinct from other types of paper. Compare it against typical printer paper for a reference.

Coil Paper & Gum Type Designations

The Plate Number Coil Study Group has defined a classification of paper types for coils as follows: Type I, Type Ia, Type II, Type IIa, Type III, Type IIIa, Type IIIb, Type IIIn, Type IV and Type Vn. These classifications have been utilized in this Tagging Project for paper types.

Paper Type I

When exposed to LW UV light this paper will show some presence of optical brighteners in varying degrees of brightness. Color of paper under LW can range from dull purple to bright purple-white. Some brightener is always present, even if only as small luminscent fibers. Backlighting can be used for identification since it has a 20° crisscross pattern, though some Type I stamps show no criss-cross pattern. The gum has 45° diagonal gum ridges.

Paper Type I

When exposed to LW UV light this paper will show some presence of optical brighteners in varying degrees of brightness. Color of paper under LW can range from dull purple to bright purple-white. Some brightener is always present, even if only as small luminscent fibers. Backlighting can be used for identification since it has a 20° crisscross pattern, though some Type I stamps show no criss-cross pattern. The gum has 45° diagonal gum ridges.

Paper Type Ia

A smooth-textured trial gum found on examples of 20c Consumer Education coil P# 1 & 2 and 18c Surrey from P# 9, 10, 13 & 14.

Paper Type II

When exposed to LW UV this paper will appear “Dead” with a color of brown/yellow-brown with no optical brightners or luminescent threads. Gum texture is smooth in with faint horizontal striations in appearance. The paper has a rough surface texture viewed from stamp face. Backlighting is can be used to identify this paper since it has a 45° criss-cross pattern.

Paper Type IIa

Type II has all the same characteristics as Type II accept for gum texture. Gum texture has striations that are distinctly heavy appearing as evenly spaced horizontal ridges.

Paper Type III

When exposed to LW UV this paper will appear “Dead” with a color that is a darker, deep purple-brown color when compared against Type II. Backlighting will show no diagonal paper texture appearing smooth and uniform. Gum texture is stippled or a wavy horizontal pattern. The paper has a smooth surface texture viewed from stamp face compared to other paper types.

Paper Type IlIa

This paper can only be differentiated by its gum, which is uniformly smooth and yellowish next to Type II gum.

Paper Type IIlb

The gum on this paper is fairly smooth with subtle horizontally oriented striations. A strip of three or more stamps makes viewing the striation patterns much easier since the striations fade in and out across the gum surface.

Paper Type IIIn

The distinct characteristic is the gum, which has subtler ridges running at an approximately 56° angle.

Paper Type IV

This paper was the first phosphored paper used on the Transportation Series and the first phosphored paper with dull gum. The gum is uniformly smooth in appearance. This paper is only found on the 23c Lunch Wagon P# 2 & 3.

Type Vn

This paper has diagonal gum ridges like Type I or Type IIIn with embedded phosphor appearing mottled in shortwave UV. It is only found on the 23c Lunch Wagon P# 3.