J.CAC VOLUME 38 (2013)
Iron Stain Removal from Archaeological Composite Artifacts made of Wood and Iron
When some composite wood-iron artifacts from a marine archaeological site became stained by iron corrosion products during storage, a procedure had to be developed to remove the staining from the wood surface. Eight solutions were evaluated to determine how well they could remove rust stains from paper (a convenient form of cellulose). The solutions included a combination of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA), oxalic acid, thioglycolic acid, sodium dithionite with and without a chelating agent (EDTA), poly(vinylpyrrolidone) (PVP), and phosphoric acid with and without PVP. The most effective of these, sodium dithionite plus EDTA, was then tested further. It was found that the dithionite solutions should not be heated or exposed to air; that other chelating agents can be used instead of EDTA, such as DTPA or the sodium salt of N,N-di(2-hydroxyethyl)glycine (DHEG); that the concentration of chelating agent is not critical; and that the results are similar whether the sodium dithionite and chelating agent are used in the same solution or used sequentially in separate solutions.
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