Help me clean this coral/spongel up

[Sberebit]

I would like to clean the surface of this coral to try and remove the dirt. The dirt is really embedded (i.e., not removable with water alone). How would I go about doing this?

[Ptychodus04]

How hard is the material you are trying to remove? One side of the coral looks like it is begging to fall off already so anything you do needs to be gentle.

 

I would start by seeing what you can pull off with a dental pick.

[Sberebit]

3 hours ago, Ptychodus04 said:

How hard is the material you are trying to remove? One side of the coral looks like it is begging to fall off already so anything you do needs to be gentle.

 

I would start by seeing what you can pull off with a dental pick.

The material I'm trying to remove is stuck on there pretty good. I have had no luck with the dental pick. Any other suggestions? I'm willing to experiment or try whatever.

[Ptychodus04]

1 hour ago, Sberebit said:

The material I'm trying to remove is stuck on there pretty good. I have had no luck with the dental pick. Any other suggestions? I'm willing to experiment or try whatever.

Try a drop of vinegar on it and see if it fizzes. You have to be careful not to dissolve the coral itself, but you can often remove a matrix if it is limestone based without detriment to the fossil with short soaks in vinegar.

 

Without specialized prep equipment like a micro-abrasive system, you're kind of limited on ways to attack it.

[Sberebit]

11 minutes ago, Ptychodus04 said:

Try a drop of vinegar on it and see if it fizzes. You have to be careful not to dissolve the coral itself, but you can often remove a matrix if it is limestone based without detriment to the fossil with short soaks in vinegar.

I'll give it a shot. Thank you for your help.

[Sberebit]

16 hours ago, Ptychodus04 said:

Try a drop of vinegar on it and see if it fizzes. You have to be careful not to dissolve the coral itself, but you can often remove a matrix if it is limestone based without detriment to the fossil with short soaks in vinegar.

 

Without specialized prep equipment like a micro-abrasive system, you're kind of limited on ways to attack it.

What I did was spray it with cleaning vinegar and got no reaction (no fizzing). Should I soak the whole fossil in the vinegar to see if it reacts with the vinegar? If so, for how long? Thank you.

[Natalie81]

Maybe rewoquat can do the trick? We had good results with that. @Ptychodus04, what do you think? 

[Ptychodus04]

39 minutes ago, Sberebit said:

What I did was spray it with cleaning vinegar and got no reaction (no fizzing). Should I soak the whole fossil in the vinegar to see if it reacts with the vinegar? If so, for how long? Thank you.

If you didn’t get a response from the small application of vinegar, the soak probably won’t make a difference.

27 minutes ago, Natalie81 said:

Maybe rewoquat can do the trick? We had good results with that. @Ptychodus04, what do you think? 

If the matrix is clay based, rewoquat or potassium hydroxide might make a difference but I don’t suspect that is the case based on how hard the stuff sounds

[Sberebit]

1 hour ago, Ptychodus04 said:

If the matrix is clay based, rewoquat or potassium hydroxide might make a difference but I don’t suspect that is the case based on how hard the stuff sounds

You are probably right. With that said, I do have some clay based fossils that could use a cleaning.