The Wet and Dry Printing Methods on U.S. Stamps

A Blowup of a Portion of the  10¢ Special Handling Stamp  Wet Printing -  Scott QE1a A Blowup of a Portion of the  10¢ Special Handling Stamp  Dry Printing -  Scott QE1 The above illustrations show that there is a distinct difference in quality between the wet and dry printings. These are both exceptional examples chosen to illustrate the point. Note that the Special Handling stamps were printed on the flat plate presses only. As discussed below, it is not always possible to make the determination of "wet" or "dry" from the sharpness alone. We have copies of the 25¢ stamp that approximate the quality of the stamp on the right above. However, the 25¢ stamp was not printed by the dry method. This illustrates the difficulty in making the determination of wet or dry by examining the sharpness of the printing. Other means of differentiating the wet and dry stamps are needed and are outlined below.   Wet Printings Dry Printings 1. Printing is not razor sharp 1. Printing is sharp and crisp to the point of being      almost proof-like (particularly on rotary press) 2. Dull, rough printed surface 2. Hard smooth sheen 3. Thinner paper - from .0030 to.0034 inches 3. Thicker Paper - from .0037 to .0042 4. Offsets on gum side common 4. Offsets on gum side unusual 5. Gum is slightly yellow, thicker, smooth      and often shows grooves (both) 5. Gum is nearly white, thinner, rougher      and does not show grooves (flat plate only) 6. Displays overall tone in the color of the stamp (both) 6. Does not display overall tone (rotary press only) 7. Smaller than dry printing by as much as     .25mm (flat plate only) 7. Larger than wet printing by as much as     .25mm (flat plate only)

A Plate Single of the 25¢ Air Mail Stamp of 1947  Rotary Press - Wet Printing -  Scott C36 A Plate Single of the 25¢ Air Mail Stamp of 1947  Rotary Press - Dry Printing -  Scott C36a

The above illustrations clearly show the difference in color between the wet and dry printings on the rotary press stamps. Note the overall "toning" on the wet stamp (left). The reasons for this are discussed below. You might wonder why we have used plate singles to illustrate the point. Scott lists the plate numbers that distinguish the U.S. stamps that were printed by both the wet and dry methods. If your stamp has a plate number attached you can use this information to separate the stamps. About the Wet and Dry Printing Methods Although the term "dry" printing suggests the paper was dry, the paper used in the dry printing method actually contained about 5%-10% moisture content while the traditional "wet" method used paper with a slightly higher 15%-35% moisture content. The average U.S. collector might think that the first "dry" stamps were certain Liberty Series stamps of 1954, but this is not the case. The first U.S. stamps printed using the dry method were the Flags of the Overrun Countries of 1943-1944, printed by the American Bank Note Company. Although experiments at the Bureau of Engraving and Printing began in February of 1949, the first U.S. stamps printed using the dry method were the 8¢ Liberty bi-color of 1954, and shortly thereafter the Lewis and Clark commemorative, the $2 Duck Stamp of 1954-1955, and the $1 Presidential bi-color ( Scott 832c). The dry printings used a fast-drying non-offset ink, crucial to the process and promised great savings in the printing of bi-color stamps. How to Distinguish Wet and Dry Printings The flat plate stamps used the same presses for both the wet and dry printings, while the rotary press printings used a Stickney press for the wet printings and experimental new presses for the dry printings. This necessitates a different approach to distinguish wet and dry printings for each printing method. In all cases, however, a much greater pressure was needed to get the ink to print properly on the "dry" paper, resulting in the surface of the dry stamp being harder, smoother, and shinier than the duller, rougher surface of the wet stamp. But the overriding factor, and this is the main factor in the determination of wet Vs dry, is that the stamp design is clearer and sharper on the dry printings. This is particularly true for the rotary printings, to the point that the stamp is almost "proof-like", but it is also true to some extent for the flat plate printings. Additionally, the dry printings used a thicker paper, .0037 to .0042 inches versus .0030 to.0034 inches for the wet printings, and this difference in thickness may prove noticeable to an experienced collector. Because the dry printings used a quicker drying ink (of different composition), there will often be a noticeable color difference between the wet and dry printings of the same stamp. The slower drying inks of the wet printings had the further effect of adding offsets to the sheets of stamps placed above. If a used stamp has an offset on the back there is a high likelihood the stamp was printed using the wet method. As mentioned, a different approach is needed for the rotary press and flat plate stamps. The following provides a few guidelines. Rotary Press - Wet Vs Dry Printings For rotary press stamps, the wet printed stamp may display an overall "tone" in the same color as the stamp. This will rarely be seen on a dry printed rotary press stamp. This overall "tinting" is seen on both wet and dry flat plate printings however, and will not distinguish wet and dry flat plate printings. Flat Plate - Wet Vs Dry Printings The gum on the flat plate wet printings was applied by the Bureau after the printing, while the sheets used for the flat plate dry printings were pre-gummed. The wet printings, with the gum applied after the printing, have a thicker layer of smooth gum that may appear slightly yellowish and show grooves, whereas the pre-gummed sheets used for the dry printings, with gum applied by the paper manufacturer, is nearly white, has a rough texture and never shows the cracks and grooves of the BEP applied gum. The rolls of paper provided for the printing of rotary press stamps were not pre-gummed, so any difference in gum will not distinguish wet and dry rotary press printings. On the flat plate printings the added pressure of the dry press actually stretched the paper somewhat. Along with the fact that the wet method usually resulted in some shrinkage, the wet and dry printings may show a difference in size as much as a quarter mm. This difference in size may be all the proof that is needed to determine whether the stamp is "wet" or "dry". Let us emphasize that this difference in size is only readily discernible on the flat plate printings.

Suggested further reading: A contemporary series of running articles on the new (at the time) dry printing method  by George W. Brett , Sol Glass and Norman W. Kempf - The Bureau Specialist - Volumes: 25-30. Printed by the Bureau Issues Association

 

 

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