The Challenge of Look-Alike Stamps
Many postage stamps share identical designs, colors, and denominations, yet they represent entirely different issues with vastly different histories and values. To distinguish these varieties, collectors must look beyond the surface design and analyze the physical production characteristics of the stamp. Two of the most critical factors in this analysis are the printing method used to produce the image and the watermark embedded within the paper.
By systematically evaluating these physical attributes, you can accurately identify complex stamp varieties that appear identical at first glance. Utilizing digital tools like StampSnap can assist you in organizing your findings and creating a likely identification record for your collection as you work through these physical tests.
The Four Major Printing Families
According to the American Philatelic Society, there are four major printing families used for postage stamps: line-engraved intaglio, gravure, letterpress, and lithography. Line-engraved intaglio is a recess process where ink is transferred from deliberately incised lines on a plate. Gravure is also a recess process, but it forms tones using screened cells rather than hand-engraved lines.
Letterpress, a relief process, transfers ink from raised surfaces to the paper. Lithography, specifically offset lithography, is a planographic process where the image is formed on a smooth surface, utilizing oil-based ink that adheres to the image area before being transferred to a rubber blanket and offset onto the paper. On modern stamps, more than one of these processes may be combined, making a methodical approach essential.
Analyzing Printing Clues with Non-Contact Magnification
To identify the printing method, collectors should use non-contact magnification under diffuse or oblique light. Line-engraved intaglio designs are normally constructed from lines, hatching, cross-hatching, and stippling. Under oblique light, raised ink can sometimes be seen on the surface, and the printing pressure may leave debossing on the reverse. However, these are supporting features rather than single definitive tests.
Modern offset lithography commonly combines separate process-color layers made from very fine dots. While modern lithography can be incredibly sharp—meaning soft or blurred edges are not a dependable identifying rule—you must interpret dot patterns carefully. Screened or raised effects can appear in other processes, such as gravure, so collectors must combine multiple visual observations and consult production records rather than diagnosing a process from dots or softness alone.
The Role of Watermarks in Stamp Production
When printing methods do not fully differentiate a stamp, watermarks often provide the final clue. Watermarks are security measures incorporated into stamp paper to deter counterfeiting. They consist of words, letters, or symbols formed from dies attached to the frame used to make paper from pulp, resulting in thin places in the paper.
Some stamps exist on both watermarked and unwatermarked paper, or on paper with entirely different watermarks, which generally receive separate catalog numbers. Consequently, a watermark can be the sole difference between a common stamp and a highly valued variety. For example, U.S. stamps of the late 19th and early 20th centuries often feature double-line or single-line "USPS" watermarks that are critical for proper cataloging.
Safe Watermark Detection Techniques
While some watermarks can be read by holding the paper up to a light source, many stamps require more sophisticated study. The American Philatelic Society recommends laying the stamp face down in a dark tray and moistening it with commercial watermark fluid, such as Clarity, which is safer for your health and your stamps than other chemical options.
The fluid evaporates quickly and will not impact the gum on an unused stamp, bringing up the watermark in dark lines against a lighter background. This dipping process is also highly useful for detecting hidden faults like thins, creases, and tears. While optical devices like the Safe Signoscope or Morley Bright Watermark Detector exist, traditional watermark fluid remains a highly reliable method for most collectors.
Synthesizing Your Findings
Identifying a complex stamp variety requires combining all cumulative clues. First, examine the printing method under non-contact magnification, noting whether the design features the raised lines of intaglio, the screened cells of gravure, or the fine dot patterns of offset lithography. Next, safely submerge the stamp in watermark fluid to check for paper variations, such as the double-line "USPS" watermark used from 1895 to 1910 or the single-line "USPS" watermark used from 1910 to 1916.
Once you have gathered these physical clues, you can consult a standard catalog to find the correct variety. You can then use StampSnap to log the stamp, keeping a clean, organized digital record of your specialized collection and ensuring your physical findings are preserved for future reference.
Frequently asked questions
How do I tell the difference between line-engraved intaglio and gravure?
Use non-contact magnification under oblique light. Line-engraved intaglio features raised ink lines, hatching, and stippling, and may show debossing on the reverse. Gravure is also a recess process but forms its tones from screened cells. Because screened effects can appear in multiple processes, you should combine these observations with production records.
Is it safe to use watermark fluid on unused stamps with original gum?
Yes, if you use a safe, commercial watermark fluid such as Clarity. It evaporates quickly and does not damage or dissolve the gum on unused stamps. Avoid using household solvents or water, which can damage the stamp or dissolve the gum.
Can I identify a printing method based solely on the softness or sharpness of the design edges?
No. Modern offset lithography can be extremely sharp, meaning soft or blurred edges are not a dependable rule for identification. You must treat visual features as cumulative clues and combine them with other evidence, such as dot patterns and production records.
What is the best way to view a difficult watermark on a U.S. stamp?
Lay the stamp face down in a dark watermark tray and moisten it with a few drops of commercial watermark fluid. This brings up the watermark as dark lines against a lighter background. This method is particularly helpful for faint single-line "USPS" watermarks, which can be very difficult to see otherwise.