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Cleaning Lithic Artefacts

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  • Cleaning Lithic Artefacts

    What is Patina and do I Clean?


    Patina on chert is caused by carbonic acid from atmosphere that causes desilisification on the surface of chert, at the same time microbes invade microfractures and start eating the chert while metabolizing other nutrients and produce a metabolite which is silicified. These metabolitic by-products and microbes die leaving a micro-residue. Minerals, silica acid precipitate and fossilize the microbial residue to produce semi-crystalline biopolymers. These biopolymer structures are not completely crystalline and have a lot of defects in the lattice and void dislocations.

    To take a good look at the patina or lack of one needs at least a 10X scope. I used a microscope that can go up to 30X.



    Come on, Jack, nobody can really read that, hahaha. The simple answer to the question "What is patina on an artifact?" is: Silicified dead microbes and microbe poop!(as Doc Gramly puts it)


    Whenever non-collectors have asked me what patina was, I've always told them "the scum of the ages." Sounds like I was closer to the truth then I realized.


    Here's saltwater/beach/midden patina on a Columbia point made of FL chert as found. I do not recommend oiling artifacts and the oil was removed completely with acetone after this experiment: Click image for larger version

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    Here's the same point after 12 hours in mineral oil, soaking through the patina: Click image for larger version

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    After 30 hours in oil: Click image for larger version

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    Click image for larger version

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    Yep, patina is old rot and sometimes a build up on top of that.

    Would be nice for some to post pics of broken points that show the depth of some patinas. I have never seen a Paleo in FL without thick patina, unless it's been rolled around in a river or from a wet site. Even our Woodland points often have the same white patina from sand/soil. But the heaviest patina is on Paleo-Early Archaic around here, and that is generally 3-6 feet down in sand. Patina will also be different on one side sometimes because of the way it laid in the ground or on the ground. On some paleo items the process is so advanced that the items become chalky instead of glassey. Ugly, but old as dirt. I've seen points with solid patina on one side and blasted glassy from sand on the other, from being exposed, same with some points that have laid out on a beach or another site for a long time, though it doesn't take long for some patinas to change. Saltwater causes particular different patinas on our points, too.


    Tom - I would have to assume that soaking a point in oil would also affect its value, yes? But it sure makes a difference in appearance. I usually just wash mine under running water and scrub with a toothbrush. I checked out a local pawn shop that has artifacts for sale and noticed that most of their points are clean and shiney. Do you think they've done something to make them that way. Most that I find are dull but may have a semi-gloss appearance. ---Chuck


    It doesn't hurt the value as mineral oil comes out with acetone bath. You never should oil an item made of porous, lesser-grade, or some other types like slate, other rocks... material. It works on high grade agate, chalcedony, cherts here. Really just about the same rocks, mineralogically speaking..!

    Here's after 6 hrs acetone, post oil: Click image for larger version

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    After about 24 hrs it was gone. Oiled points often just glaze back over, over time. Some collectors have backlit, oil encased frames with translucent coral points in them. White patinated points here can be almost any color from heat treating chert and coral.

    I prefer them natural, once in a while I like to just see how pretty they were. If they look shiny in a shop might be sprayed with clear craft spray (ugh!) or just recently oiled.


    Chuck / Tom

    A lot of the old time collectors oiled their points. They also used varnish to make them gloss up. I have used acetone to clean oil & varnish off more than a few.

    I have seen a display case that was made to hold mineral oil and the artifacts were suspended in the oil. It was pretty cool as the case was back lighted and the artifacts were made of translucent agatized coral so the light bounced through them. Gomer has that case full of the Bat Wing Cache he found. I think there were 23 total. Need to look it up.

    When I am lucky enough to find an artifact all I do is removed by hand the surface dirt. I never wash them. I want some dirt left on them so you can see what type of soil it was found in. The soil will tell an authenticator a lot about an artifact.



    Jack - Thanks for that piece of advice. I had been taking painstaking care to make sure I got all the dirt off my finds but now I'll just wash them under running water and get the chunks off. Never thought about the dirt being used as a authentication issue. ---Chuck


    Here is a picture of the Bat Wing Cache, that Gomer found. Click image for larger version

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    I bought two pieces from an auction that were clear coated. I'm like you guys I hate that look! What your saying is acetone will take the shine off and not hurt the point?



    You can use paint thinner to take the varnish off, it will not hurt the point.



    Truly great education guys thanks. Here is one for you Jack, have you ever heard of artifacts being sprayed with hairspray?? There was an old timer in Homeworth, Ohio used to spray his points with "Aquanet" hair spray!! I remember as a youth they looked awesome, but does it hurt the point?? I would think that it would come off easier than varnish. Not thinking about doing it just wondering if anyone else has heard of it before-Bill


    >>>wmwallace wrote:
    Truly great education guys thanks. Here is one for you Jack, have you ever heard of artifacts being sprayed with hairspray?? There was an old timer in Homeworth, Ohio used to spray his points with "Aquanet" hair spray!! I remember as a youth they looked awesome, but does it hurt the point?? I would think that it would come off easier than varnish. Not thinking about doing it just wondering if anyone else has heard of it before-Bill<<<

    Bill, I do know that "Aquanet" will kill poison ivy patina! LOL


    Sorry, Jack, but I have to disagree. The soil left on or put on any point tells nothing about the point. I'd be very worried about any authenticator that espouses any great knowledge about dirt. Dirt is easily and readily added to modern points, but it tells nothing about the point. On your personal finds, a person could take a simple soil test to tell about the site's soil, whatever good that might do. But the miniscule dirt particles on your finds won't say much about the point itself, other than maybe a general sense of the soil color and texture in the particular site. Dirty points must be cleaned before examination, and dirt fools more collectors (and authenticators) than just about any other foreign substance. JMO.


    Thanks for the tip Paul, I might have to try that out next time I come across the old PI. Never got it as a youth, as I age like everything else seem to get more allergies and afflictions. Just sprayed a crop of it coming up in my front flower bed-Bill



    Yes I heard about using hairspray, which is a type of varnish, if you think about it. Look at Donald Trumps hair, it is heavily varnished. LOL.




    I do not scrub the soil off with water but remove the majority of it with a soft brush or by hand on my personal finds. If I send one of my found points to an authenticator I want them to see some of the dirt it was found in.

    If someone sells me an artifact that was said to be found in area that I know is a red dirt area I would expect to see some sign of that red dirt in the cracks and crannies. If not red then a red flag goes up.

    If an artifact is found in an area of caliche a layer of clay or sand containing minerals such as sodium nitrate and sodium chloride I would expect to see this in the cracks and crannies.

    As the majority of my collection is not personal finds and have been bought I have more than a few frames of scrubbed down artifacts.

    Yes you can add dirt to and I know that is a common practice with the fakers.



    I guess I used to go to extremes to clean points before I understood the meaning of Patina. Thought Patina was the shine or river wash then. I guess you can't clean Patina away but it is easier to fake Patina these days. I just brush them with warm water and call it good now Joe.



    You can over scrub an artifact. You can remove some of the surface mineral deposits if you are too aggressive in cleaning them. I used to just wash them in water, but now I use a dry soft brush to remove the dried soil.



    I use a worn out soft bristle toothbrush with one drop of dishsoap. Purdy hard to wash off thousands of years of patina.


    Patina will not be removed but some surface mineral deposits can and do get removed if cleaned to hard.


    [J.M. McCrary]:

    What is the best method to clean your artifacts? I have been using water and toothbrush, but there is probably a better method so was interested to hear how others clean their own.


    same here for 47 years water and a soft bristle tooth brush.


    x2 good ol tooth brush....




    Yep! Same here... Toothbrush!


    Me too!


    Another hint. If you find one in a creek with creek stain, try to get it off before it dries.

    [J.M. McCrary]:

    >>>rmartin wrote:
    Another hint. If you find one in a creek with creek stain, try to get it off before it dries.<<<

    Good timing considering in a couple hours I was going to try the walking the creek by my usual spot. Thank you for the tip!


    I was told by a collector at a relic show if there is heavy mineralization try vinegar, a spray hose (sink or bathtub), and/or liquid fabric softener.


    I agree with Hoss, been lookin for about 45 years now and water and tooth brush work great. I'd be leary of trying anything more as you could wash off some of the "patina"!
    Last edited by painshill; 01-30-2016, 06:41 PM.
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