Hat tip to Joe Marino of the Shroud Science Group for this quote from an article by Cullen Murphy in Harpers, November 1981:
Theories abound as to how the shroud could have been concocted, and STURP is forever testing new ones, if only to keep the project fun. Should some member be seduced by the notion that the image was formed by an elusive combination of butter, lemon, and egg yolk, the team would immediately go into action, devising experiments, creating simulacra, baking the coated samples, irradiating them with lasers, burning them with acids, working feverishly until an excited phone call informed coordinators Jackson and Jumper that, while the mixture didn't yield an acceptable shroud image, it made a remarkably fine Hollandaise sauce."
The Harpers article is very informative and entertaining. You can find it in libraries. You can also find it online at http://www.harpers.org/archive/1981/11/0024680 but you will need to subscribe to the magazine to read it. The cost is $16.95 per year.