Yes, I am a bad girl. I occasionally use acid to prep my fossils. Some people are absolutely against acid prep. Lots of fossil hunters use it.
What constitutes acid preparation?
So many of our fossils are limestone based. Lime Away works!
Most toilet bowl cleaners work to clean off the top layer of matrix from the fossil.
Vinegar works to dissolve some matrixes, very gentle in my opinion.
However, my personal favorite is Muriatic Acid. A gallon is about $5 at any hardware store. It is commonly used for cleaning and etching concrete, removing mortar from bricks, and “brightening” concrete and masonry.
How to use Muriatic Acid:
USE ONLY PLASTIC CONTAINERS AND BRUSHES, USE PLASTIC/RUBBER GLOVES, PROTECT YOUR EYES AND SKIN!
Used almost exclusively on hash plates.
A 20% solution in a spray bottle does wonders to bring out the details in a hash plate. Rinse with lots of plain water in an area that you don’t want anything to grow again – like a gravel driveway. Expect some fizzing and fumes.
You can dunk a fossil into a diluted solution of Muriatic Acid and water. Expect a fair amount of fizzing and fumes (do this outdoors). Soak in water afterward. This water will now be a diluted acid dunk – just an FYI. 😀
Fossil wash bay and acid dunk bay.
You can use a plastic dish pan with a straight Muriatic Acid solution, dunk the fossil for from 5-30 seconds, dunk in another pail and then another pail. Use a plastic brush to agitate the matrix off in the last two pails. Harsh, I know! But to be honest with you, I have found most of my trilobites in hash plates this way.
Plastic syringe and metal needle.
I have used a needle and syringe (Fleet Farm in the farm section) to draw up straight Muriatic Acid and put it on a specific fossil that I am trying to get a look at or to remove matrix as surgically as possible beside a fossil.
Bad, bad girl that I am… I have even poured straight Muriatic Acid on fossilized hash plates outside and rinsed them off with a hose. Sure brings the brachiopods and other fossils hiding there out!
WARNING! WARNING! WARNING!
This stuff can blind you if splashed in the eyes! Wear eye protection!
It WILL eat off the top couple of layers of your skin if allowed to contact it. Protect your skin! And yes it will ruin most shoes.
It will kill plants.
DO NOT allow your pets around when working with it! We are talking LOTS of water dilution if working outside and you have cats, dogs or kids.
What fossils do not react well to acid?
Crinoids & bryozoans MELT!
Trilobites may bleach and lose distinctive markings.
