Rotary Press Identification

Is using tracing paper or thin foil another identifier for rotary press stamps? Would a standard flat exhibit any image if traced? I have attempted this and one of my Washington's has a good amount of detail coming through and I can not get anything coming through on a few others. Just wondering if this is another good identifier, along with the other typical identifiers. Thanks for any help!

I think the "template method" explained in the link below works best:

http://www.1847usa.com/FlatPlateVsRotary.htm

Great. Thanks! I actually jus found something out about the tracing paper method on that site too! Thanks WT1!

The tinfoil test is used to help differentiate between offset and rotary/flat plate printings. Offset printing doesn't create any raised areas on the paper. Rotary and flat do. The ways to determine flat from rotary include design size differences, line printing quality (thinner lines), and color to help differentiate between two Scott #s if they didn't share the same color.

For line quality differences: Rotary is on the left, flat plate on the right.

Thank you for that very descriptive post, Historical!

Flat plate and rotary are two types of intaglio printing, i.e. by the use of engraved plates. Intaglio, or "engraving," is the name of the printing method, and the other two terms refer to the plate format. But more than this, the foil test is a test for "relief printing" as opposed to "surface printing." One makes an impression on the foil, one does not.