How many letters does the top answer for “an autographic device to test the strength of raw silk.” have?

The most common answer is serigraph (9 letters).

Crossword clue: an autographic device to test the strength of raw silk.

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

serigraph 9 letters web-def

a print made using a stencil process in which an image or design is superimposed on a very fine mesh screen and printing