How Do You Dissolve Limestone

[DE&i]

I’m trying to extract more of these…what appear to be teeth whether they are shark or fish I don’t know at present but am working my way around to their I.D. . . . these kindly fell out but I have a lot of this material I’d like to test sieve to see what else there may be .

They were set in Limestone which is quite crumbly I think it’s called the Blisworth Limestone, Great Oolite. Would anyone know how I could dissolve the limestone some more…would warm slightly soapy water be sufficient.

Regards,

Darren.

[creto]

I would use vinegar. It is cheap, easy to find and will not damage the teeth.

[Coco]

I'm OK with Creto : vinegar or Acetic acid (with water !). I think it works better if your limestone is dry at first.

But pay attention not to inhale the émanations !

Coco

[DE&i]

Coco...Creto...thats interesting, I use a malt vinegar with a 6 percent acidity level to help prep my bone finds . You say water some vinegar down Coco any particular quantities and any particular length of time to soak the limestone.

Darren.

[Coco]

I rarely use vinegar, but I think you can try with 1/2 wather and 1/2 vinegar. If the action isn't rather fast, you can add some vinegar.

About acetic acid, I think you can put 70 % wather and 30 % acetic acid.

You have to Watch the fossil which you so soak, because some limestones are more or less slow to dissolve. thus you try with an unimportant part, you take off 5 mn later to see what takes place, and you put back in the liquid by watching.

The liquid shouldn't exceed half of the basin, because that should be going to make bubbles and small projections. Best is to use these products outside.

Coco

[Boneman007]

KoH (Potasium hydroxide) is also very good at removing limestone.

[DE&i]

Thank you all for the speedy response that’s given me the push to leap into action. I’ve gone for the careful approach with a small sample in diluted malt vinegar. And it’s very gently bubbling away I’ll keep you posted.

Darren.

[creto]

Darren, I would not dilute the vinegar. If you want to speed up the process you can heat the vinegar. I just put some into the microwave and get it fairly warm and it goes much faster.

[DE&i]

Darren, I would not dilute the vinegar. If you want to speed up the process you can heat the vinegar. I just put some into the microwave and get it fairly warm and it goes much faster.

I think you may be right Creto my experiment seems to have ground to a halt ill leave it over night then reassess it in the morning.

Thank You,

Darren.

p.s. would you mind if i may ask , have you had some good results using this method could you show me any finished pieces.

Edited May 20, 2013 by D&E

[Ramo]

You might want to look up fellow member Marco Sr. He has developed a method where he uses boiling acid, freezing, thawing, boiling, etc that breaks down very hard limestone. I'm sure you could use his methods to break down your matrix.

Ramo

Oh, I forgot to mention that those teeth look like pycnodont teeth to me.

Edited May 21, 2013 by Ramo

[Bev]

I have a couple of shares on this...

Lime Away, Sno-bol, and other toilet bowl cleaners work well.

Also, I have used a muratic acid bath very effectively.

Use a plastic container (dish pan) for both. Clean with water. Best if done outside. Both will discolor stainless steel--just sayin' if you have a SS sink. DON'T dump any of the remains down you sink!

And I have found a stainless steel "toothbrush" from the paint store to do wonders in general cleaning.

Bev

[DE&i]

You might want to look up fellow member Marco Sr. He has developed a method where he uses boiling acid, freezing, thawing, boiling, etc that breaks down very hard limestone. I'm sure you could use his methods to break down your matrix.

Ramo

Oh, I forgot to mention that those teeth look like pycnodont teeth to me.

Hi Ramo,

Thank you for your advice ill look Marco Sr up . You would be correct in saying they are pycnodont teeth , ive even managed to find what genus ( Eomesodon ) but to what species i still dont know. I cant find any reference to anybody else find finding teeth such as these from the same area!

Darren.

[DE&i]

I have a couple of shares on this...

Lime Away, Sno-bol, and other toilet bowl cleaners work well.

Also, I have used a muratic acid bath very effectively.

Use a plastic container (dish pan) for both. Clean with water. Best if done outside. Both will discolor stainless steel--just sayin' if you have a SS sink. DON'T dump any of the remains down you sink!

And I have found a stainless steel "toothbrush" from the paint store to do wonders in general cleaning.

Bev

Hi Bev,

Thank you for the very informative method we have similar cleaning products here in the UK im just amazed they can whittle away at Limestone but leave the fossils untouched.

Darren.

[Ludwigia]

If worse comes to worst you can drop it into 10% diluted hydrochloric acid. That works pretty quick, but you have to make sure that the object you want to save doesn't dissolve away as well. There are tables to tell you which substances are immune, for instance silicified fossils like the corals from Nattheim. Afterwards the fossils should have a long bath in soapy water (alkaline) to neutralize any remaining acid. Oh, and don't forget your rubber gloves and tongs and do it in the fresh air because of the fumes.

Oops! I just realized that Bev's muriatic acid is a synonym for my HCl. Well, better double than nothing...

One more important thing. Pour the concentrated acid into the water and not the other way around, otherwise it'll get rather hot and explosive...

Edited May 21, 2013 by Ludwigia

[bone2stone]

KoH (Potasium hydroxide) is also very good at removing limestone.

Caustic aproach I like that.

[Herb]

Boiling the matrix in TSP or automatic dishwasher xls in water will also weaken soft matrixes. Vinegar is only a 4 or 5% solution so don't dilute it.

[Socket]

I might be a little late but just from my experience.

I use an 8-10% buffered acetic acid. I have used vinegar straight from the bottle in the past. Some people will take the rock out of the solution every 24 hours and wash it under the tap to expose a new surface. I try not to do this because you can risk damaging the smaller fragile fossils. I prefer to gently 'shake' it a bit when it is in the acid.

Be careful though. Acids can 'etch' fossils if too strong. If it starts really bubbling away, you may want to add more water, Acids can attack the fossil preferentially if the limestone has a low cement content or dolomitised. You can avoid etching by coating the fossils in a runny super glue. It will impregnate the fossil and strengthen it. You can always remove it with acetone. Just wait 24 hours for the rock to dry then 24 hours for the super glue to dry.

Another couple of points,(some have been mentioned above).

- You can stabilise the rock with modelling putty or plasticine. I have had rocks dissolve rather quickly in the past and put pressure on the fossils as they have broken down.

- Warm water with the acetic acid will speed up the process

- Wash the specimens very well in water when they are taken out of acid.

- Avoid tipping strong acid down the drain. Not going to mention names but a certain famous institution literally dissolved all their pipes away after employing a large scale acid digestion program.

- A 250 μm sieve size will trap the smallest microvertebrate and conodont (if you decide to break down palaeozoic and triassic rocks) fossils.

Edited June 29, 2013 by Socket

[DE&i]

Hi Socket,

Your never to late with this much needed advice I'll be collecting Bathonian limestone again in next years field trip program so im making notes all the time to help me sieve through this difficult matrix.

Darren.