Ok, I've been picking up a ton of CAD I, AN hardware for an upcoming project and I have noticed a lot of these old bolts are dyed a red(majority), purple, or green color. I have heard that this was applied to ID the bolt as one that had undergone magnaflux testing. Can anyone confirm this? I have specifically heard that red meant a certain percentage of a lot was checked (i.e. 1/1000 bolts etc.) and that green meant that all the bolts had been checked. That is why you see red dye on smaller bolts and Green on larger ones. Is this true? I have a 1941 copy of "Magnaflux Aircraft Inspection Manual" by Doane and Thomas and it refers to a "red paste designated as No. 9, which has become available during the past year [1941], and its use is growing rapidly". This is a liquid paste suspended in oil used in the magnaflux testing process, could this be the residual red dye that I see on my bolts? The manual says the paste is to be washed off, but that the rinsing process may leave residual paste. If anyone has any insight into the subject I would be excited to hear it as I want to be 100% original in its application, origin, and use on other hardware items. Thanks.
Taylor
me109me109@aol.com