Ethnographic Arms & Armour - View Single Post

vilhelmsson · 13th February 2019, 07:01 AM

I found this post while researching a Petersen type M axehead I received as a gift for Christmas this past year. It was purchased from the same place that your axehead was purchased.

Your axehead is really cool looking.

After further research, here are my findings.

TL;DR: It was treated with rust converter; it could be authentic or it could be a more modern reproduction. Very hard to more precisely date it without some surface destructive analysis.

The axehead has been conserved with rust converter; the eye is harder to apply the rust converter to. The most common rust converters use tannic acid to convert iron oxide (i.e., rust) into the bluish-black ferric tannate and simultaneously apply a protective primer layer. You can find more information on the wikipedia page at https://en.wikipedia.org/wiki/Rust_converter.

A bi-product of the process is that the rust converter fills in macroscopic pores (though it is generally microscopically porous as discussed in the articles I link to below) and pits, and smooths out the surface corrosion of the artifact. So there might have been warts and wrinkles before it was treated.

The US National Center for Preservation Technology & Training (NCPTT) calls rust converters "a reliable avenue for protection" of rusty fences, grates, car parts, artwork and collectibles. They are in the midst of a multi-year study, and here are links to the study initiation and their first round of results:
https://www.ncptt.nps.gov/blog/mater...nvertor-study/
https://www.ncptt.nps.gov/blog/compa...st-converters/

There is a lab that I like to send more expensive items to for XRF testing. I recently asked them about conducting XRF testing of items treated with rust converter. Here is an edited version of their response:

"We are happy to take a look, the rust converter (typically Paraloid B (https://en.wikipedia.org/wiki/Paraloid_B-72) I believe) should cause issues with the XRF process. We have had issues where the patina or some surface level incrustation causes issues getting good results. Typically if we own the piece we'll clean off a very small section to get better results."

13th February 2019, 07:01 AM	#17
vilhelmsson Member Join Date: Feb 2019 Location: Bay Area Posts: 57	I found this post while researching a Petersen type M axehead I received as a gift for Christmas this past year. It was purchased from the same place that your axehead was purchased. Your axehead is really cool looking. After further research, here are my findings. TL;DR: It was treated with rust converter; it could be authentic or it could be a more modern reproduction. Very hard to more precisely date it without some surface destructive analysis. The axehead has been conserved with rust converter; the eye is harder to apply the rust converter to. The most common rust converters use tannic acid to convert iron oxide (i.e., rust) into the bluish-black ferric tannate and simultaneously apply a protective primer layer. You can find more information on the wikipedia page at https://en.wikipedia.org/wiki/Rust_converter. A bi-product of the process is that the rust converter fills in macroscopic pores (though it is generally microscopically porous as discussed in the articles I link to below) and pits, and smooths out the surface corrosion of the artifact. So there might have been warts and wrinkles before it was treated. The US National Center for Preservation Technology & Training (NCPTT) calls rust converters "a reliable avenue for protection" of rusty fences, grates, car parts, artwork and collectibles. They are in the midst of a multi-year study, and here are links to the study initiation and their first round of results: https://www.ncptt.nps.gov/blog/mater...nvertor-study/ https://www.ncptt.nps.gov/blog/compa...st-converters/ There is a lab that I like to send more expensive items to for XRF testing. I recently asked them about conducting XRF testing of items treated with rust converter. Here is an edited version of their response: "We are happy to take a look, the rust converter (typically Paraloid B (https://en.wikipedia.org/wiki/Paraloid_B-72) I believe) should cause issues with the XRF process. We have had issues where the patina or some surface level incrustation causes issues getting good results. Typically if we own the piece we'll clean off a very small section to get better results."