Suggestions on Echinoids preparation

[Reg]

Hi there folks,

 

I need help and advices on how to prep some echinoids that I have found on calcarenite matrix. I am new in fossil prep plus I know these kind of calcarenites are very sneaky to treat. In the picture below there is a Scutella subrotundae before and after a quick prep-test I did with a couple of nails. The problem now is to take away the sand grains very close to the shell. Which technique should I try to follow now? I am thinking to the digestion in cold acetic acid, which I know it is used to extract microfossils from limestones and calcarenites, but I do not know if it works with macro stuff too.

 

Thank you in advance,

Daniele

[LabRatKing]

Don't use acids on this. They will destroy the fossil and won't harm the matrix one bit!

 

First order of business is to stabilize the fossil with a liquid penetrate polymer. Lots of ways to do this in the fossil prep thread.

Once treated and cured, then its mechanical removal time. Air abrasion is boss, but manual peck and scratch will do the trick too.

[Reg]

11 hours ago, LabRatKing said:

Don't use acids on this. They will destroy the fossil and won't harm the matrix one bit!

 

First order of business is to stabilize the fossil with a liquid penetrate polymer. Lots of ways to do this in the fossil prep thread.

Once treated and cured, then its mechanical removal time. Air abrasion is boss, but manual peck and scratch will do the trick too.

 Ok, Thank you very much. I will go and take a look on how to use liquide penetrate polymer. Cheers!

[minnbuckeye]

Hello! Wonderful specimen. I have collected many echinoids in Florida. Though I am by no means an expert, here is what I suggest. Most of my specimens cleaned up well with just a stiff wire brush and a razor blade. Occasionally, the assistance of a dremel engraver was needed. Nothing special, which is nice!!  The echinoids did NOT need stabilization with a polymer as they were not fragile. If hand cleaning is to be done, the polymer will make it harder to remove the matrix. By the way, your specimen looks great as is. I like seeing a bit of the matrix attached. It tells a bit about where the fossil came from. Good luck. 

 

 Mike

 

 

[Reg]

On 12/13/2020 at 1:57 PM, minnbuckeye said:

Hello! Wonderful specimen. I have collected many echinoids in Florida. Though I am by no means an expert, here is what I suggest. Most of my specimens cleaned up well with just a stiff wire brush and a razor blade. Occasionally, the assistance of a dremel engraver was needed. Nothing special, which is nice!!  The echinoids did NOT need stabilization with a polymer as they were not fragile. If hand cleaning is to be done, the polymer will make it harder to remove the matrix. By the way, your specimen looks great as is. I like seeing a bit of the matrix attached. It tells a bit about where the fossil came from. Good luck. 

 

 Mike

 

 

Hi Mike, thank you for your advices. Thank you also for your appreciation on the specimen. So I have proceeded using a dremel engraver to remove the coarser matrix and the result is good, despite the process took time. The problem is the fine removing of matrix attached to the shell. It is super difficult to remove this matrix. This matrix is strongly mineralised I think because of dissolution and precipitation of calcium carbonate close to the shell. I have tried different nails to remove it but a razor blade was the best. But as you can see the final result (see picture below. right: before prep; left: after prep) is not as good as I hoped. 

[Huntonia]

I think this piece looked excellent in the before picture on the right. Some of prep work comes down to assessing your skills and materials and deciding if further work may be beneficial or detrimental.

 

I wouldn't recommend using a razor blade for fine detail work on this kind of a delicate surface. Abrasion would probably be the best method, but you can try brushes and running water (presuming the fossil isn't too fragile for this).

 

If the brushes aren't effective and you don't want to dive into air tools I'd recommend using a very fine tipped hand tool under strong magnification. This method will be very slow but you should be able to chip off the tiny bits of remaining matrix without harming the fossil. Hope this helps 

[Ludwigia]

@Reg Just for future reference: Some collectors, particularly the Swiss ones, like to use caustic potash plates to dissolve matrix clinging to calcified fossils. This substance does not disturb the fossilized shell. The fossil is placed in a metal container and then the matrix to be removed is covered with the plates and then a few drops of water are added to them until they soften up. It is a process which takes a long time and sometimes needs to be repeated several times, but it is generally trustworthy and effective. Sorry I didn't notice this post earlier.

[minnbuckeye]

Looks like you have  made great improvements to already nice specimens!!! @Ludwigia, you specifically say metal container. Is it truly preferable over plastic when using KOH flakes?

 

 Mike

[Ludwigia]

3 hours ago, minnbuckeye said:

Looks like you have  made great improvements to already nice specimens!!! @Ludwigia, you specifically say metal container. Is it truly preferable over plastic when using KOH flakes?

 

 Mike

As far as I know it doesn't really matter. You can also use ceramic.