Cleaning Fossils With Vinegar

[obsessed1]

I have cleaned the matrix off of fossils with vinegar before but never had any issues until this time. As the matrix block with fossil is drying there is some almost crystal looking objects growing onto the fossil and parts of the matrix. My guess is that there is still some vinegar in the matrix that the fresh water soak did not get out. I soaked the block for about 16 hours in clean water after the matrix had been cleaned off of the fossil. Any ideas on how to stop the action of the vinegar?

[sweeneyb]

I have cleaned the matrix off of fossils with vinegar before but never had any issues until this time. As the matrix block with fossil is drying there is some almost crystal looking objects growing onto the fossil and parts of the matrix. My guess is that there is still some vinegar in the matrix that the fresh water soak did not get out. I soaked the block for about 16 hours in clean water after the matrix had been cleaned off of the fossil. Any ideas on how to stop the action of the vinegar?

Yes i have experienced the same problem when I clean my echinoids. I dried them off and put them in a case next thing you know it looked like salt had formed on them.

[Guest N.AL.hunter]

Very mild baking soda solution and then rinse, rinse , rinse.

[Frank Menser]

Very mild baking soda solution and then rinse, rinse , rinse.

Yep....

[Xiphactinus]

good rule of thumb -- you need to rinse (or soak in plain water) at least 4 - 5x longer than the fossil was in the vinegar. The white powder is an indication that the acid is still active and with humidity adding the water, your fossil is slowly being eaten.

[silverphoenix]

yep, baking soda and rinze--gotta neutralize the vinegar before the fossil is decalcified any further...that's why I use H2O2 instead of acids--turns to harmless water and does not de-mineralize the specimen. Good luck with that.

[obsessed1]

Well..I soaked it in a baking soda solution for an hour which got rid of the white powder right away. It has now been soaking in clean water for almost 4 hours. I will take it out tomorrow evening and see what happens. Thanks to all who gave advice on this problem.

[MikeD]

Well..I soaked it in a baking soda solution for an hour which got rid of the white powder right away. It has now been soaking in clean water for almost 4 hours. I will take it out tomorrow evening and see what happens. Thanks to all who gave advice on this problem.

A few additional rinses with fresh water wouldn't hurt.

[obsessed1]

should I shorten the soak time and add some more rinses or leave the soak time the same and just add more rinses?would putting it in a tub and letting water run over it constantly for several hours work better?

[silverphoenix]

Whatever your water bill can handle lol

Really, a few hour soak and 3 or 4 rinses will 100% ensure that any trace acid is removed.

[Crinoid Queen]

Yep....

Yup baking soda

[lordpiney]

im not sure what would happen to the fossil, but ammonia totally neutralizes all acids.

[silverphoenix]

im not sure what would happen to the fossil, but ammonia totally neutralizes all acids.

Well besides the smell, I'm not quite for sure what ammonia would do to a fossil and to what composing minerals...but natural is always the way to go on this stuff--use as very little chemicals as possible. I'm not a chemist and don't know what does what/reacts or neutralizes what, so I always stick to plain ole H2O and H2O2 at most--makes life simpler and it's easier on both the fossils and the lungs

[Shamalama]

I always stick to plain ole H2O and H2O2

Will that help in dissolving away excess carbonate, or just help with the overall cleaning process? I've always thought of Hydrogen Peroxide (H2O2) as being good for a disinfectant, but not as a cleaner of rocks.

[Pool Man]

Is there a difference in using apple cider vineger vs White vineger? And I know peroxide is a good oxidizer, and will clean any remaining organics off,but I will have do a PH test on some to see if its acidic and will affect the matrix.

Dan

[ashcraft]

I use acids fairly often to clean fossils, but I use them on material where the fossil is silicified, which won't react with the acid, leaving only the matrix limestone to dissolve. If I was going to clean a carbonate fossil in limestone (which are basically the same material), I would spot apply the acid, with a brush or a hypodermic needle.

Acid neutralization is best achieved with baking soda, which forms a base in solution. It is cheap and non-toxic. Also doesn't produce toxic fumes with acids.

If you want to "kick it up a notch" with acids, go to the hardware store and get muriatic acid, or mason's acid. It eats limestone like me and cherry pie. It gives off some nasty fumes though (chlorine gas), so do it outdoors. It will not dissolve silicified fossils. It is what the Smithsonian uses to prep large blocks.

Brent Ashcraft

[Pool Man]

Be very carefull with muriatic acid.Its just a weaker version of hydrochloric acid. I have had jet black fossils leave a black residue on my hands and get etched very heavily, im my experiments with the acid.

Dan

[ashcraft]

Keep in mind that vinegar is a 6% solution of acetic acid. Pure acetic acid is known as glacial acetic acid, and has an INTENSE smell of funky feet, I pass some around to students to whiff, and invariably someone will take a big snort, and head to the toilet. Acetic acid will dissolve about anything that muriatic acid will, but slower, because it is a "weak" acid (nothing to do with strength of dissolving, rather with how it dissolves in water).

Muriatic, or hydrochloric acid, is actually a gas, and is the acid found in your stomach. It will come in concentrations to around thirty percent, which is the most that will dissolve in water. It is the ULTIMATE carbonate dissolver, (which is what is in many stomach antacid tablets), and if your fossil has any carbonates in, or around them, it will dissolve it. It is also heck on elemental iron, and some iron salts, and will dissolve other metals to a slower extent. It is a useful tool for dissolving large blocks of limestone with silicic fossils, removing matrix, but not harming the fossils.

The black material could have been MnO2, which (as I recall) is fairly insoluble in HCl, possibly locked in a carbonate matrix, that the acid would dissolve.

It is a powerful tool, that should be used with caution.

Brent Ashcraft

[silverphoenix]

Will that help in dissolving away excess carbonate, or just help with the overall cleaning process? I've always thought of Hydrogen Peroxide (H2O2) as being good for a disinfectant, but not as a cleaner of rocks.

H2O2 is great in the overall cleaning process and will get dirt and looser matrix off by infiltrating the matrix and expanding. It is 100% non-damaging to carbonate and silica alike.

I wasn't thinking about those fossils found in limestone matrix, as I never have that problem myself (all found "free" in matrix and not "trapped" in a limestone or sandstone)--now thinking about what you would use on those particular instances, White (distilled) vinegar is the only thing I would consider using. Again, this is because I am not a chemist and do not care to be one--that was my Least favorite subject last semester and one I barely survived. Same in high school...

Anyways, if you are to use the distilled vinegar on limestone matrix (red wine vinegar is good for salads, apple vinegar is good for fish--neither I'd recommend for fossils), I would Not soak the entire fossil in it. When I last prepped a limestone fossil using vinegar (nice nautiloid from leakey, TX), I made a paste using baking soda and water and covered the fossil with a thin coating, then used an eye dropper to apply the vinegar to the matrix--being careful to stay at least a 1/2cm away from the edges where the fossil began. I then let it sit for a couple hours, worked at it with a tiny screw driver (substitute for dental pick) scratching away the weakened limestone until I couldn't anymore and then repeated the process. It's slow going, but very controlled and safe. The baking soda dries and makes a "shell", which will both neutralize any acid that touches the fossil, and at the same time letting you know that vinegar has gotten that far. I guess you could spot treat with vinegar and leave it on for a good while, reapplying of course, but I have no idea how long it would take because I was too impatient to do this. Baking soda will just wash completely off and will do no damage.

Vinegar is a very weak acid as has been stated, but it's all I have experience with and would use--if you want faster results, then a stronger acid might be the key--but remember that if you use a stronger acid, the results are unpredictably fast and what fumes would be given off, I have no idea. The reason these stronger acids are used by museums and labs is that they often have large amounts of limestone to remove, but for a smaller specimen as what you're dealing with, in my humble opinion, I'd use something slower acting like the vinegar.

[ashcraft]

Attached is a photo of what you can do with a little acetic acid (50%, about 10x stronger then vinegar), a dental pick, and an abrasive blaster. It is about 2/3 finished. The crinoids are about the size of a dime, and are ailicified. The limestone is from the Girardeau, an Ordovician deposit. I posted a "waste" piece picture some time ago, this is the main slab. Be jealous, be very, very jealous.

The acid king,

Brent Ashcraft

[Guest N.AL.hunter]

Very nice. Can't wait till it is finished. And if you are the "acid king", are you married to Tina Turner? Now let's see who the heck knows what I am talking about.

[Shamalama]

The jealousy quotient is definitely high!

[Pool Man]

Anyways, if you are to use the distilled vinegar on limestone matrix (red wine vinegar is good for salads, apple vinegar is good for fish--neither I'd recommend for fossils), I would Not soak the entire fossil in it.

Does anyone else have an opinion on the white vineger VS apple cider vineger? The white Vineger is cheaper than the apple cider, but it was specificaly recommended to me,by a couple of people here, to use on the stuff I find off the beach. I'm usually trying to remove barnacles and encrustations. So far the apple stuff has worked great. But if I can save a buck a gallon, then all the better.

Dan

[jkfoam]

Does anyone else have an opinion on the white vineger VS apple cider vineger? The white Vineger is cheaper than the apple cider, but it was specificaly recommended to me,by a couple of people here, to use on the stuff I find off the beach. I'm usually trying to remove barnacles and encrustations. So far the apple stuff has worked great. But if I can save a buck a gallon, then all the better.

Dan

Dan,

Go with the plain vinegar and save the money. It is the acetic acid content of the vinegar that is doing the work on the calcium carbonate. I think the only difference between regular vinegar and apple cider vinegar is the flavors in the apple cider vinegar and the flavors don't react with calcium carbonate.

[tracer]

yeth - i hast an opinion. many of them agshully, which is prolly why i'm online instead of with all the friends i don't have. oops. sharing too much again.

my beef with apple cider vinegar is that is it such an extremely perfect health potion that it agshully reverses aging, which will have two negative effects if you keep using it. first is that you'll eventually be back in diapers, and second is that your fossils are gonna end up being from the wrong period, epoch, eon, or whatever they call whenever they're from.

ok, i actually have more beefs with apple cider vinegar. by using it, you're depriving others of apples, and they will therefore have to go to the doctor more, which is driving up health care costs. so basikly you're the cause of all the need for health care reform.

my tertiary (or have i gotten to quarternary yet?) beef is that you're supporting those who are cynical and misguided enough to turn perfectly good ethanol into acetic acid. my recommendation to you is that if you were to simply imbibe the ethanol prior to it's conversion to vinegar, then you wouldn't care about the barnaclees and encrustaceans, and if you imbibed enough, you could go look at your fossils and enjoy having two of each one.

so anyway - here's my final ants swear. all vinegar is made from fermented something or another. white vinegar is just distilled regular vinegar. i would think the acetic acid content is the main issue, which might run like from 4 to 8% in distilled vinegar. i'm sure some vinegars are higher, but the only difference there in my mind would be the length of time you can let the object soak to achieve the same result.

if i were going to use vinegar, i would try to use the cheapest vinegar i could find. but i prefer air abrasives.