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Paraloid B-67 is an isobutyl methacrylate polymer that dries harder than Paraloid B-72. Industrially, it is used as an impregnative barrier for rust-prone metals to protect them, e.g. in automotives.
It is hydrophobic, providing excellent water resistance (a suitable sealant following Pyrite Decay treatment in Pyrite Stop). It can provide an excellent barrier against both atmospheric moisture and gas (oxygen); with much lower permeability than Paraloid B-72. Storage in low humidity environments remains essential, but Paraloid B-67 can provide an extra barrier layer between atmosphere and fossil.
Paraloid B-67 can be used as a coating or penetrant sealant for pyritic fossils. With its hydrophobic (water-repelling) properties it is a better candidate for this than Paraloid B-72. Moisture, whether atmospheric or liquid, is one of the main factors in pyrite decay. Paraloid B-67 is also removable as it is redissolvable in solvent, and so it can be used and then removed prior to another round of treatment in Pyrite Stop (ethanolamine thioglycollate).
For this application, we have a 10% solution premixed in acetone. You may need to further dilute this in acetone depending on the fossil. Acetone provides the best clarity of solution, speed of evaporation and impregnation capabilities for this application. It is not usually suitable for archival marking.
We absolutely recommend storage in a low humidity and low oxygen environment even after coating with Paraloid B-67. Learn more here about preventing pyrite decay.
Prolonged exposure to UV light will cause yellowing, but in thin coatings this is unlikely to be noticeable. It can be removed with solvent and reapplied.
Not to be confused with the more commonly used Paraloid B-72, which is chemically very different, and used as an adhesive and consolidant.
In archaeology, it is used to stabilise bone, clay, stone and other fragile artefacts. It is used outdoors for artefacts and monuments that require a hydrophobic (water repelling) coating.
UK Mainland (excludes NI) customers only due to restrictions on shipping. We also have available in our shop the pellet form, which will allow you to purchase acetone and mix yourself with acetone purchased locally to you.
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