How do I stop destroying the center of my ammonites?

[MrFrog]

Hi, first post to the forum. 

 

I have been practicing prepping with my Dremel 290 on my charmouth ammonites.

 

The outer keel always works alright but I loose it when I get into the center and I keep ruining them.

 

Anyone have any tips? Any other methods I can use when it comes to the center. I've tried using hand picks but the stone seems too hard.

 

I'm going to try dripping ascorbic acid on it to loosen it but in past experience it dulls the detail and colour.

 

Any tips much appreciated.

 

Many thanks.

[Ludwigia]

I could imagine that by the looks of the photo the problem with your ammonites might be that the centers are not preserved, which makes it difficult to know when to stop.

[Ptychodus04]

Take a look at https://www.zoicpaleotech.com/

 

They sell fossil prep styli for the dremel scribes. Also, use magnification when you prep, if you aren’t already.

 

If the inner whorls are there, both of these will help keep you from blowing through them. Also, learning to prep comes at the expense of many fossils.

[FossilDAWG]

Ascorbic acid is Vitamin C, which will not do anything to dissolve carbonate rock.  Acetic acid will, as will hydrochloric acid.  However these acids require great care to use, and in your case they will certainly dissolve the fossils which are made of calcite.  There is no acid that would be of any use on these fossils.

 

The suggestions regarding Zoic tools are the ones to pay attention to.  I have these tips and they can work well.  You have to work under magnification, stopping frequently to clean the area you are working on so you have a clear view.  Sometimes wetting the area (damp, not dripping wet) can improve contrast between the matrix and the fossil, making it easier to see what you need to remove.

 

Don

[SPrice]

MrFrog, I, too, use the Dremel 290  with the Zoic tungsten tips for prepping fossils, besides other tools. Those tips make all the difference.

 

The posts above have given you the best advice and tips, IMO,  so I can't really add much to those.  But there has been one bright light bulb

 

technique that has really helped improve my results.   While I don't have any Charmouth ammonites, I do have a variety from Europe, the Jurassic

 

Coast of England and many dozens from local Cretaceous areas in Utah, USA.

 

The technique is both simple & challenging - dial the Dremel down to 1 or 2 max and use the lightest pressure possible. It's almost like you're

 

trying  not to touch the matrix at all. Just let the vibrating stylus get close and the chips and flakes fly off. It sounds contrary to logic but it works

 

for me.  In the beginning of removing matrix I do add a bit of pressure and then when working along the fossil itself, I just let the tool do its job

 

without any noticeable pressure.  Takes a lot of practice to not push the tool.  

 

Steve

Edited September 22 by SPrice

[jpc]

As others have mentioned... magnification is the key to doing a good job on the inner whorls of ammonites.  Preferable a binocular microscope. but a standard magnifying  lamp might be good.  

[Jaybot]

On 9/22/2024 at 12:58 PM, jpc said:

As others have mentioned... magnification is the key to doing a good job on the inner whorls of ammonites.  Preferable a binocular microscope. but a standard magnifying  lamp might be good.  

Something like a opti-visor works well too.