By Aaron Gibson,
MS, Environmental
Toxicology/Epidemiology

Muriatic acid is a commonly used chemical to lower pH in swimming pools, etch concrete, and clean masonry surfaces. In the routesetting world it is better known to us as a way to clean climbing holds. The advantages of muriatic acid are that it is relatively inexpensive and very effective. It quickly cuts away chalk, rubber build-up, and oils and leaves a sparkling clean hold that requires little to no hand scrubbing.

Unfortunately, very few gyms that use muriatic acid employ all the controls necessary to ensure that their cleaning operations are safe for gym personnel and the environment. Furthermore, use of muriatic for hold cleaning has many additional effects that may leave you thinking twice about dunking your holds in it.

Quick Chemistry

Muriatic acid is the historic name for hydrochloric acid (HCl) in water. It’s basically industrial strength stomach acid. It is generally sold as a solution of approximately 30% HCl to 70% water. The most common solution for hold cleaning is a 10% solution in water. It varies based on concentration, but generally speaking an off-the-shelf bottle of muriatic acid requires a mixture of ten parts water to one part acid to reach a 10% solution. This means for every one cup of acid you should have ten cups of water. And don’t forget: add acid to water, NEVER water to acid.

Health Effects

Let’s think about this logically for a minute: if muriatic can get all that gunk off your climbing holds, what do you think it can do to your body?

Muriatic acid can cause redness, irritation, and burning of your skin. For that reason you should always wear gloves. And not just any gloves, you need some gauntlet-style acid-resistant gloves. Those little latex gloves you’ve been using? Those won’t cut it. Especially when you reach you hand in the bucket a little too far and the water/acid solution fills your glove up to the brim.

And what about your clothes and shoes - do you want holes in them? How many people wear a protective apron or vinyl-coated coveralls and rubber boots to keep the splashes off your duds, not to mention your skin underneath? Should you get acid on your skin the treatment is to rinse it thoroughly for a minimum of 15 minutes.

Your eyes are an extremely delicate part of your body – vapors can easily be absorbed through your eyes. Even low concentrations of muriatic acid splashed in your eyes can severely damage them or render you permanently blind. For that reason eye protection in the form of approved safety glasses/goggles should always be worn.

Even if you skip every other piece of advice do not skip this – wear eye protection.

The vapors emitted from muriatic acid are noxious. There is a high potential for inhalation exposure when you are pouring from the bottle during the initial mixture/dilution phase with water. If inhaled, muriatic acid can burn the lining of the nose, throat and lungs. For this reason you should always have good ventilation. In most cases this means working outdoors. Barring this, a NIOSH approved respirator should be worn along with filter cartridges suitable for acid mists. My hunch is that a few people are wearing off-the-shelf dust masks for protection – those do not provide any protection against acid vapors.

Gym Issues

Muriatic can damage metal – meaning, if you wash it down the drain enough times pretty soon your plumbing will corrode. Never pour muriatic acid down your gym drain, sink, or storm drain – it can cause serious corrosion to pipes. Instead, neutralize the acid using baking soda or lime. This should be done in a separate bucket by adding the baking soda or lime first and then slowly adding the used muriatic solution. Make sure you wear a respirator or have good ventilation when doing this as noxious fumes can be generated.

All businesses (including climbing gyms) that maintain chemicals on hand are required to maintain Material Safety Data Sheets (MSDSs). These forms may be included when you purchase the chemical or are readily available online for downloading and printing (for free). The MSDS form provides physical data about the chemical and provides information on how to safely handle and work with the substance. To find an MSDS online just Google the manufacturer of the chemical you have and the word “MSDS.”

Environmental Considerations

Muriatic, if dumped outside, can impact local waterways and vegetation and be toxic to aquatic life. If you choose to dispose of your left over muriatic outside be sure that it is fully neutralized and heavily diluted with water.

But I know you. You’ve read all this and you’re still thinking, “Yeah – but it cleans so well!” Of course it does – but maybe too well. Prolonged use of acid to clean holds damages them over time. Depending on the strength of the solution a single washing leads to increased corrosion of washers and deterioration of hold texture. In fact, holds that have been exposed to muriatic acid cleaning multiple times are often left with a greasy, glossy feel due to their erosion of texture.

For these reasons the negatives of using muriatic acid far outweigh the positives. So let’s explore some safer alternatives:

· Hand cleaning – Good old-fashioned biodegradable, non-toxic dish soap and scrub brush will do the job. If you only have a few holds to clean at one time or if you have a bunch of people to help clean this is a good choice. The disadvantage: time consuming and labor intensive.

· High pressure sprayer/power washer – This is becoming a more popular method for many gyms. No soap needed, no scrubbing. Disadvantage: needs to be done outside and must have a power washer and supplied water.

· Dishwasher – Easy to throw a batch of holds in, add some biodegradable/non-toxic dish detergent, set the timer and forget about them. Least labor intensive. Disadvantage: requires a dishwasher be on-hand, uses more electricity, limited load size for cleaning, quality of cleaning varies based on the dishwasher model.

Muriatic acid can be used safely and effectively if all safety and health controls are in place. But most gyms and gym employees responsible for cleaning holds rarely implement all the controls and often use none of them. Not only is this dangerous for the employee but it can be a liability to the gym.

Muriatic and water must be accurately measured to achieve the correct concentration so as not to damage the holds. Even when measured correctly, some brands of holds may be affected more than others. With a number of alternative safer methods available for hold cleaning, muriatic acid should not be your first choice. Choose a different method and save the muriatic for swimming pools.

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