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Any secrets to removing red clay?


Sacha

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There are lots of locations in the country where the fossils we collect are found associated with red soil or persistent red clay. This isn't a rust stain, but the very fine grains embedding themselves on the porous surface of the fossil, in the following picture the subject is specifically echinoids. Is there a secret way of removing this coloration? The Wythella eldridgei are particularly fragile, so I was concerned about ultrasonic cleaning or heavy scrubbing. Any tips?

 

DSCF1641.thumb.jpg.d6d722d5a125480f6e4858cc7b02bcf6.jpg

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Well if we told you, it wouldn't be a secret anymore!

 

I wonder if you would get any reaction on those echinoids from a soaking in Hydrogen Peroxide.  Marcos Sr. told me a good tip to soak the "micros" in it to dissolve and dislodge the stubborn matrix particles.  

I have tried it on several different fossils I have and they clean up with pretty good success.

Maybe you could try it on a lesser one to experiment.

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27 minutes ago, caldigger said:

Well if we told you, it wouldn't be a secret anymore!

 

I wonder if you would get any reaction on those echinoids from a soaking in Hydrogen Peroxide.  Marcos Sr. told me a good tip to soak the "micros" in it to dissolve and dislodge the stubborn matrix particles.  

I have tried it on several different fossils I have and they clean up with pretty good success.

Maybe you could try it on a lesser one to experiment.

 

I tried 3% for a short time and got no reaction. I expected to see bubbles. The sand dollar was still wet. Maybe I need to get the hightest strength and soak overnight. 

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Not sure what it is, but if the reddish color is caused by iron oxide you could use the Waller solution: http://www.johnbetts-fineminerals.com/jhbnyc/articles/minclean.htm

 

The "Waller" Solution

This method of mineral cleaning was first introduced to me by Roland Franke as a simple method of cleaning iron stain from minerals. Further research reveals different methods of using the basic solution.

As originally described by Roland the solution is made by dissolving in one liter of distilled water:

8.4g Sodium Bicarbonate

17.4 g Sodium Dithionite

5.9g Trisodium salt of Citric Acid (sodium citrate)

Once mixed, the minerals are immersed in the solution. The cleaning action can be accelerated by placing in an ultrasonic cleaner. This solution is not appropriate for indoor use because, once mixed, there is a strong odor of rotten eggs. Use only outdoors or in an area with proper exhaust venting. As usual, read all precautions on the individual component packages.

The solution is good for only about 24 hours and should be discarded after that. Since a liter of the solution may be more than you need, the Geological Museum of Copenhagen (Hansen, 1984) suggests a variation - you can prepare a stock buffer solution of one liter water, 28 g sodium bicarbonate and 59 g sodium citrate (citric acid). Then when ready place your specimens in a container, pour in buffer solution to cover the top, then carefully sprinkle on top 1 g sodium dithionite for every 30 ml of buffer solution. After five minutes another 1 g of sodium dithionite is added in the same way. They also recommend sealing tightly with a lid and keeping at room temperature to avoid the formation of sulfides and sulfur.

If you have heavy iron stain a specimen may require several treatments in succession as the solution becomes saturated and loses effectiveness. After your piece is clean then wash in distilled water for an equal amount of time that the specimen was in the solution. Then in running (or regularly changed) tap water.

Apparently, the solution works by reducing Fe+3 to Fe+2 and then dissolving Fe+2 in the Citric Acid. The Sodium Bicarbonate balances the pH to be neutral. This last point means that theoretically, you can clean any mineral in it without worrying about etching it. Practically though caution should be taken by testing on samples prior to immersing your best piece.

 

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Be not ashamed of mistakes and thus make them crimes (Confucius, 551 BC - 479 BC).

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Ok...or you can just go get some "Iron Out" at the hardware store.

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Very informative but not applicable. Not iron staining , but red clay particles imbedded in the porous structure of the fossils.

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Soak it if it can handle it -- dental picks with 10x magnification. Pick it off a grain at a time. Hours of tedious work, therefore, only prep the ones worth the time. I would definitely prep the big one. How many more is up to you. Do you think you'll find more that are in better condition? Soon? For sure?

 

 

Mark.

 

Fossil hunting is easy -- they don't run away when you shoot at them!

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1 hour ago, Mark Kmiecik said:

 Do you think you'll find more that are in better condition? Soon? For sure?

 

Only time will tell. Will certainly give it a shot.

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Just now, Sacha said:

 

Only time will tell. Will certainly give it a shot.

What I meant by those questions is that if the chances are quite good that you'll find a better specimen soon don't bother putting in the time to prep the lesser one. That time, which can be hours, is better spent looking for more fossils. Of course you need to hunt a location a few times before you have a good idea of what it will probably produce, but sometimes even only one trip can hint at the possibilities.

 

 

Mark.

 

Fossil hunting is easy -- they don't run away when you shoot at them!

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I don’t know if I agree with that. These alllook like really nice specimens and worth a little tlc.if they were mine I’d try a soft bristled tooth brush maybe even one of the ones for babies and some gently moving water.maybe a trickling faucet over a bowl just in case. But take my advice with a grain of salt. I don’t believe there is such a thing as an unworthy fossil. Also if he does it at night even for a few minutes he’s not losing any fossil hunting time LOL! Also I love prepping (I’m weird I know) so I don’t consider time spent prepping anything as wasted

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7 hours ago, Sacha said:

Very informative but not applicable. Not iron staining , but red clay particles imbedded in the porous structure of the fossils.

 

From https://sciencing.com/red-clay-22940.html :

Clay Composition:
Clay particles contain silica (SiO2) and a mixture of other minerals, such as quartz, carbonate, aluminum oxides and iron oxides. The ratio of SiO2 to other clay minerals within clay determines clay type. Continued weathering of clay causes leaching of minerals, such as sodium, potassium, calcium and carbonate, but iron and aluminum oxides are more stable and less likely to leach out. Highly weathered clay deposits contain mostly aluminum or iron oxides, the minerals in red clay.

You can't remove the clay but possibly the red color.

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Be not ashamed of mistakes and thus make them crimes (Confucius, 551 BC - 479 BC).

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I'd try the peroxide again. Dry the fossil thoroughly before soaking--wet clay is pretty impermeable to aqueous solutions, but dry clay should soak it right up. At least in theory; I haven't tried much with peroxides.

 

I've also seen something called Rewoquat (marketed as Varisoft in the US) recommended for breaking down clay minerals. I haven't tried that yet, but it might help.

 

Good luck!

 

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On 7/10/2019 at 4:35 PM, Sacha said:

Very informative but not applicable. Not iron staining , but red clay particles imbedded in the porous structure of the fossils.

Iron oxide is what makes red clay red. It might work.

 

 

Mark.

 

Fossil hunting is easy -- they don't run away when you shoot at them!

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  • 3 weeks later...
On 7/10/2019 at 9:35 AM, caldigger said:

Ok...or you can just go get some "Iron Out" at the hardware store.

 

As an update to this topic, a warm solution of Iron Out does in fact quickly remove direct rust stains from echinoids and it also bleaches out the red color of the clay, but much more slowly. I'm rinsing the cleaned pieces and there seems to be no detrimental effects from the Iron Out solution. Once again, thank you Doren for the easy fix!

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