When you are first getting into rock collecting, you find that there are many different ways to clean up and polish rocks, and about 10x as many opinions in the forums.
In this article, we’ll talk about cleaning rocks with citric acid.
What is Citric Acid People Use To Clean Rocks?
Citric acid is a weak organic acid that exists naturally in citrus fruits such as limes and lemons.
The manufactured form is used in multiple products, including food/beverages, cleaners, cosmetics and supplements.
In general, when you see people talking about “citric acid” as it relates to cleaning up rocks, usually they are referring to the food grade form that you can buy from the grocery store and Amazon, such as this one.
Product links in this article may be Amazon affiliate links. As an Amazon Associate, I may earn a commission from qualifying purchases at no additional cost to you.
What Does Citric Acid Do to Rocks?
What citric acid may or may not do to your rock honestly depends on the rock, and what is on it.
For example, collected material is often brilliant, but also covered with stains of various colors, algae, lichen, lime, etc.
In general, folks are looking to take off the outer layers to get down to the beauty underneat.
Citric acid (like other acids) can help strip off the layers of yuck on the rock, or even take off some of the outer lawyers of the rock itself.
Is Citric Acid the Right Product To Use To Clean Up My Rock?
Citric acid may or may not be the right product to use on your rock.
I definitely don’t recommend just throwing any and every rock I need cleaned up into a citric acid solution.
For example, if the rock material you want to clean up is calcite, then soaking your material in citric acid may actually do more damage than good to your material.
Citric acid dissolves calcite.
To answer your question (which is hard to do in every case because rocks are seldom consistently made up of 100% the exact same pure substance), you need to know what it is you are trying to clean up.
Once you know what have, you can decide whether to try it in citric acid.
In general, we also recommend that you do test pieces whenever you are trying to clean up a new kind of rock or trying out a new cleaning strategy.
You’ll be able to lean what works and what doesn’t without endangering a really valuable piece.
The other thing you should know is that citric acid is not known for being a fast way to clean up rocks.
If you are impatient to get results fast, that moving to a stronger acid might be the best bet for you.
Citric acid should help clean off stubborn dirt, dissolve calcium/lime deposits, and just generally shine things up.
If your piece has some really stubborn iron staining, citric acid may not be strong enough to get the stai. completely off.
How to Clean Up Rocks With Citric Acid
If you are confident that your rocks won’t be damaged in a solution of citric acid, here’s how you would go about cleaning with it.
First, assemble your materials:
- Powdered citric acid
- Flat bottomed vessel: we like glass so you can see the materials well, and we like to use a vessel big enough that the materials have a lot of space
Next, clean your materials:
- soak the rocks in regular water
- scrub the rocks with dishsoap or laundry soap, using a toothbrush or some other small brusher
- allow the rocks to dry completely
The reason we like to let the rocks dry completely is that we can really see what’s going on with the rock, and get a baseline for where we’ve started and where we want to end up.
Take some pictures or video at this stage so you’ll be able to look back for comparison.
Prepare your solution:
- set up your vessel, I like to mix up everything where it will be sitting for the next hours/days so I don’t have to carry it around and risk dropping it (if it is large/heavy)
- measure your water as you fill up the vessel so you know how much citric acid to use
- add your citric acid to the water (not the other way around)
- add your materials to the solution –I like to use metal tongs/grabbers rather than using my hands, but you can also use gloves
In general, exactly how much citric acid to use is going to become a matter of experience and the particular specimens/look you are trying to achieve.
We recommend starting with a weaker solution first, and then moving the rocks to a stronger solution as you see whether the previous solution did its job.
For your first time, try a tablespoon of citric acid crystals per quart of water.
Watch the rocks for significant chemical reaction (lots of bubbling) which might indicate that more is happening than you planned.
If things look pretty quiet, check the rocks after a few hours, and then the next day, and the next.
If you aren’t sure whether the rocks are looking any better, pull them out of the solution and rinse them off really well with water.
Scrub them again with the toothbrush.
Let them dry and compare the specimens to the previous pictures.
If you see progress, but not quite enough, feel free to return them to the original solution.
Or, if you are impatient, prepare a slightly stronger solution.
And, as always, take good care of yourself while using citric acid.
Don’t breath in any citric acid in any form, or any fumes/vapors.
Don’t ingest it.
Protect your skin, eyes, nose, and mouth.
Don’t let children play with it or in it.
Finally, don’t mix citric acid with any other chemical or product without doing your research.
Disposing of the Solution After Cleaning Rocks With Citric Acid
When you search for this on the internet, you’ll see that a lot of helpful bloggers recommend throwing the citric acid solution down the sink or toilet.
The reason is that the citric acid solution probably contains fine particles from the rocks, or other matter that could actually clog up the pipes somewhere down the line.
Instead, we’d try and neutralize the acid with baking soda, dilute it, then pour it out outside.
There are lots of methods to clean up rocks.
We recommend that you work conservatively, learning as you go about what works and what doesn’t.
If you have more questions about cleaning up rocks, check out our knowledge hub for more related articles.