Acid Saftey

A

Augus7us

Joined
Oct 9, 2014
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I've been reading up on the various uses acid has in the knifemaking world. I picked up some ferric chloride and sulfuric acid a month ago in anticipation of needing them some day. The more I read about them the more concerned I get about safety (no experience with either). As with most things there are little 'gotchas' and one in regards to acid I read was do not pour water into acid, pour acid into water. What are some other concerns the average Joe wouldn't know about like that? I have a couple of questions to start it off:

How bad are the fumes? Is indoors ok and should I wear a respirator? If so what type of cartridge is required?

How do you guys store it? I've seen folks use it and it would appear they are storing it in a PVC pipe mounted to their bench. Seems dangerous and that it may leak fumes if not properly sealed. Concerns with this?

When neutralizing acid I've heard water, baking soda, trisodium phosphate, etc. Do these work for all acids or do they each work for specific acids? In the case of ferric chloride and sulfuric acid what neutralizes those?

Thanks in Advance!
 
The Ferric Chloride acid from Radio Shack is used for circuit boards and I have mixed with 2 to 4 parts water to etch Damascus blades. I was wearing nitrile gloves one day and was etching a blade when I touched my eyebrow because I was sweating. The next day the spot broke open and bled . It was sore as heck for a week. I still keep a bottle but I avoid having to etch anything because I don't like using acid. If I forged my own blades I would set up a ventilated place to use the acid and have tongs and wear safety gear every time. I would worry most about eye protection. Just my opinion. Larry
 
If concerned about the safety of acids you can use other acidic items that are less scary. Lemon or lime juice, tomato ketchup, vinegar, etc. will work.
 
i4Marc said:
If concerned about the safety of acids you can use other acidic items that are less scary. Lemon or lime juice, tomato ketchup, vinegar, etc. will work.
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That is correct. You can use lemon juice to etch hamons.
But do not use FeCl to make refreshing summer drinks. :D
 
FCl is pretty mundane as far as an acid goes. Handled with proper care, it is one of the safer chemicals in the shop. Store in a PVC tube with a cap slipped on it. The cap will often have to be tapped off with a piece of wood, as it fits so tight. Use it diluted 3:1 or up to 5:1 from the stock strength. Store the stock solution in a plastic acid bottle with a wide mouth. Note - DO NOT MIX the dry FC with water in the storage bottle. Do it in a large dry wall type bucket. Add the FC powder slowly while stirring. It will get hot, so allow to cool before putting in the storage bottle or PVC tube. The fumes are only a problem when mixing the powder and water...don't breathe them. Place a running fan behind you and do all mixing out in the open back yard. Don't do it on the patio or driveway, as drips will leave permanent stains on the concrete.

I don't know what you would use sulfuric acid for in the knife shop, but it is a very stabile acid as the stronger ones go. It tends to be low on fumes, but is still highly corrosive to flesh and most organic things. If you aren't familiar with acid handling and storage, I would get rid of it.

The worst acid in the shop is Hydrochloric acid ( muriatic acid). Don't let the fact that you buy it on the shelf of Home Depot in two gallon boxes fool you....this is serious stuff. The fumes will corrode/rust everything in the shop. Skin contact with this stuff is really going to be bad. Metals are eaten away. The fumes will kill you. I worked as a research chemist, and handled all sorts of deadly stuff....but HCl is one I have great respect for. Unless you have the equipment and skills needed, I would not recommend using Hydrochloric acid in the shop. For doing the final etching with a cotton ball to develop a hamon, get three quarts of distilled water and put one ounce of HCl in it. This will give you 100:1 HCl , which is quite safe. A concrete or masonry contractor will give you the ounce free.

While there are respirator cartridges for acid vapors, I would not rely on a respirator to be my safety tool. If the fumes are strong enough to be a breathing problem, they will be strong enough to dissolve in the moisture on your skin and give you a burn. Eyes are a really bad place to get acid, so always wear a FULL face shield. When working acids there are a few common sense safety procedures that will make them fairly safe to be around.
1) Know where the fumes are going. A breeze or fan from behind you is best. Work in open spaces, preferably outdoors.
2) Understand that the fumes will combine with any moisture readily. The two places on your body that are always wet are your eyes and your lungs. Acid can destroy these if you breathe strong fumes. If it makes you cough, or your eyes burn...get away from the fumes and re-think things.
3)Skin is fairly wet, too. Acid should be handles with all skin covered. Rubber gloves, long paints, thick leather or rubber shoes, long sleeves with buttoned cuffs, buttoned collars, a hat, etc.. A hood is needed for handling or using large amounts of acid, especially HCl.
4) Water is the enemy of acid, too. It dilutes it. Have a bucket of water within 5 feet when handling acid, and a hose within 20 feet. If using acid regularly, a bottle of Bicarbonate-soda water and a box of baking soda should be on hand.
5) Wash down spills with 20 times the amount of water you think was needed to get rid of the acid. Just rinsing your hands and washing them will not remove all traces. Wash with soap in running water for several minutes constantly if any skin gets acid on it. If you think a good bit of acid got on you, scrub with baking soda after rinsing for a minute, then wash and rinse for two or three more minutes. I can't overemphasize the importance of rinsing/washing for a LONG time. Many people who think all acid is gone will rub their cheek or forehead later on and get a welt. You don't even want to think about what a little trace of acid on your hands will do to your penis skin..."Honest honey, Those big red sores aren't from another woman!"
6) While having a back-up man around is a good idea when doing any task with risk, handling acid is not wise when children , pets, or company is around. Three people is a crowd with acid.
 
I have heard that hcl really eats scale on forged steel but I dont want any around my house so I may never know.
 
Household ammonia is a very good base neutralizer for acids. I do use HCL in some of my work, but it is only used outside and it's stored on the porch!
 
While HCl eats scale it's safer though takes longer if you use vinegar over night. Do the acid stuff outdoors. Have baking soda or a made up baking soda solution ready for problems . It does take time to neutralize acid as Stacy says. Face sheuid or goggles to protect your eyes.
 
Thanks Guys, especially Stacy as that was a great write up and covered a lot of my concerns!

In terms of baking soda, TSP, etc how do you prepare it as a neutralizer? Do you mix it with water and if so what ratio?

Interesting comment about the sulfuric acid. I honestly thought it was pretty common in a knife shop, at least as common as ferric chloride. I read about it somewhere, I'll see if I can dig up the article.
 
Augus7us said:
Thanks Guys, especially Stacy as that was a great write up and covered a lot of my concerns!

In terms of baking soda, TSP, etc how do you prepare it as a neutralizer? Do you mix it with water and if so what ratio?

Interesting comment about the sulfuric acid. I honestly thought it was pretty common in a knife shop, at least as common as ferric chloride. I read about it somewhere, I'll see if I can dig up the article.
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Baking soda will react with any acid to produce water and (dissolved) salt. For example, if I let HCl react with baking soda (NaCO_3) we get H_2O (water) + NaCl (salt) + CO_2 (carbon dioxide). I work with highly concentrated HCl sometimes, and I keep a small bucket of water on hand with a bunch of baking soda dumped in and stirred a bit -- about as much baking soda as will dissolve. Pouring this on acid neutralizes it almost instantly. You are better off using baking soda dissolved in water rather than powder, although the powder will work fine as well.

Also, you really need to be wearing goggles or (preferably) a face mask if you're going to work with stronger acids.
 
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Stacy, Thank you for the info. about handling acid. I didn't know very much about Muriatic acid which I was going to use for blade etching but not now. I think that since it is readily available most people think that it can't be that dangerous. You are a fount of knowledge as usual. Larry
 
Hi!
Here's my two cents about acid safety; I'm not an expert in acid etching, but I am a chemist and dangerous chemicals are my daily routine ( :cool: )
1) Correct: don't add water to any acid, they usually react strongly. But it is dangerous to pour a concentrated acid (especially sulphuric!!) in water too. If you need a less concentrated solution add the acid to the water drop by drop and let the solution cools down if it get too hot.
2) You can have different vapors working with acids: if you use chloridric acid on a metal the reaction give hydrogen which is flamable/explosive, so beware of open flames, cigarettes, etc. and it can gives off chlorine (extremely toxic gas - white/yellowihs/light green in color, extremely strong smell, irritating and lachrymatory). When using ferric chloride you usually don't get vapours; in certain condition (old, impure solutions) it may gives off chloridric acid and small amounts of hydrogen: don't breath them and work in an very well ventilated area (your kitchen table with an open window is not enough). Those fumes are toxic and corrosive, so even if you protect yourself with a respirator you don't want them around the house - this goes for EVERY acid on your list. Sulphuric acid is an annoying stuff to use, it reacts strongly with many chemicals and with skin/eyes (burns like hell!), clothes, paper, wood, rubber, plastic etc. It gives off corrosive and toxic chemicals like sulphuric anhydride. My suggestion: use ferric chloride only, sulphuric and chloridric are not safe enough for domestic use.
3) A respirator is good to have (in the lab we have ABEK filters; plain carchoal filters are not enough) but you should just stay away from the fumes and work in an open area; the respirator doesn't protect your skin, eyes (SAFETY GOGGLES MANDATORY all the time), hair, your cat, all the stuff you have in your shop, etc.
4) Store them in their original bottle; plastic bottles are fine for hydrochloridric acid and ferric chloride, glass works for concentrated sulphuric. Closed, away from children (of course), clean (you don't want to have drops of acid outside the bottle).
5) To neutralize them I suggest you to use soda; go slow with it, let it cool down, stir the mix and always wear safety goggles. Sodium hydroxide is too reactive, avoid it.

Be careful about sulphuric acid: you may have plain acid or a mixture called "oleum" which is concentrated sulphuric acid mixed with sulphuric anhydride. In case you have this one, get rid of it: it's extremely dangerous to use, very corrosive and it gives off big amount of toxic fumes.
Again, my suggestion: stick with ferric chloride, it is a friendlier chemical to use :) Get rid of the rest.
If you have any question, I'm happy to help.
 
Good info from Stacy and Olive Tree. I always assumed that Muriatic Acid was a simple and safe one. Apparently I was wrong! I have a gallon of the stuff I would like to get rid of now. What is the best way to do that? Thanks for the great safety tips! I'll stick to hot vinegar and lemon juice for etching from now on!
 
Fill a plastic garbage can 1/2 to 3/4 full of water. Dump 5# of baking soda ( you can get it in 20# bags cheap at places like Costco). Slowly pour in the acid. Let sit for10 minutes and add some more soda. If it still foams and bubbles, wait a while and add some more. Once it stops bubbling, put in the hose and let it overflow the can for a while before dumping out the rest. This is best done on the back part of the yard, in a bare spot. Done like this it won't affect the grass or plants. This will also clean you garbage can. Obviously, avoid the fumes, wear protective clothes, and a face shield.
 
This all reminds me --while in high school a student took a bottle of sulphuric acid home . On the way he bumped into something and broke the bottle !! Students do the dumbest things !!!
 
When I as in High School, a student tried to sneak out a piece of white phosphorous. He wrapped it in a wet paper towel and put it in a sandwich bag...and put it in his pocket. Later in the day it had dried out. It was literally a case of, "Liar, liar, pants on fire."
 
When I was in high school, some dumb, pretentious student (me) decided to use acids without rubber gloves because they were too thick and annoying and he was too good in the lab. So this student (always me) proceeded to analyze milk proteins with a boiling mixture of sulphuric acid and hydrogen peroxide. A single drop of that stuff fell on the student's hand and he still carries a deep, ugly scar today. Yeap, students do the dumbest things.
 
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