Oil painting cleaned with onion

A recent query by Kenneth Schaudt asked for advice about a painting
that someone had cleaned with a cut onion. I was interested to learn
that people still do this, and when I came across a pertinent
paragraph by Caroline K. Keck, in her now out-of-print book, How to
Take Care of Your Pictures: A Primer of Practical Information
(published jointly by the Brooklyn Museum and the Museum of Modern
Art, N.Y., in conjunction with the Brooklyn Museum's "Take Care"
exhibition in 1954), I thought it worth sharing. The following
paragraph is by Mrs. Keck and is quoted here with her permission:

    Cleaning Paintings with Onions and Potatoes

    Because there has been so much talk about cleaning paintings
    with onions and potatoes I wish to report that we have tried
    these two materials and that they do clean off the surface dirt.
    However, they do it less effectively than other materials and
    the hard texture of both cut onions and cut potatoes is rougher
    and tougher on the surface of a painting than a swab of
    absorbent cotton. In tests with both these vegetables we found
    it necessary to wipe off the film they leave on the surface, so
    that cotton swabs were used anyway. I had a notion that onions
    and potatoes might even clean little boys, but a violent form of
    protest prevented me from making any positive tests in this
    field.

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                  Conservation DistList Instance 9:72
                  Distributed: Friday, April 26, 1996
                        Message Id: cdl-9-72-001
                                  ***