Is Salt Water Really Effective in Neutralizing Rust on Fabric?

[Hilary Metcalf]

I am a textile artist. I transfer rust from rusty objects onto cotton fabric by spritzing the fabric with vinegar and water, then laying or wrapping the rusty object on the fabric, cover loosely and wait for the process to happen. There is a lot of 'advice' on the net about how to 'neutralize' the rust - which I assume means to arrest the process so it won't continue to eat into the fabric and cause it to degrade. The most common advice is to soak the rusted fabric in a salt water solution. I am not a scientist, so I have no idea - but I do know that exposure to salt promotes the rusting process, so I am having trouble believing that salt water also 'neutralizes' the rust. So my first question is - is this plausible? My second question relates to immersing the rusted fabric in a tannin solution. Fibre artists use a very strong brew of tea for this purpose. Artistically, this is a great process, as it creates a beautiful blue-grey bloom on the fabric and knocks back the rather icky orange colour of the rust. My research has shown that the principal active ingredient in rust neutralisers - such as you buy at the hardware - is tannin. Of course I do understand that these products are designed to be used on rusted metal, not fabric, but I assume it is the interaction between the rust and the tannin that is significant, not the substrate that the rust is on? So my second question is, if I immerse the rusted fabric in a tannin solution does that 'neutralise' the rust? And if so, what exactly does 'neutralise' mean in this context. Thank you in anticipation - and just a reminder - I am not a scientist, I am an artist, so please keep any explanation as layman friendly as possible!

 

[jim mcnamara]

For those who want a link: https://en.wikipedia.org/wiki/Tannin

I am going to reply in a non-scientific way, okay?

Tannins are in the same chemical family as resveratrol, the stuff in cool-climate red wines that is supposed to be healthy. Tannins are more of a nutrient antagonist, aptly called 'antinutrient'. Because they interfere with humans and other organisms getting nutrients from food. You can google the term. IGNORE ads!

Plants make tannins in order to prevent bugs, small animals, fungi, and bacteria from using the plant as a quick lunch. These tannin compounds are active little beasties that glom onto all kinds of other molecules and change them, making them very hard to digest. They bind to cotton, proteins, and a raft of other kinds of molecules and compounds in nature. Tannins love molecules that are nutritionally important to would-be plant munchers, like parasites.

Ever see the dark heartwood in a log? Tannins.

Heartwood has no living plant cells, and so is a target for the heartrot fungus. Nobody home to fight off the bad guys. The tree sends tannins into the Siberia of the tree to block heartrot from even starting.

So. Rust is made of iron and oxygen, and it is called iron oxide. Rust is immune to tannins. But. Tannins already glommed onto the cellulose in cotton, make the cotton immune to further interaction with rust. You can think of it as a battle between squatters. The first one to settle there stops anyone else from settling at that place.

As an artist you get the difference between a dye and a pigment. Dyes attach chemically. You cannot knock them loose easily at all. Pigments are tiny, tiny globs of color, which can attach to a fabric mechanically (or with a binder). Rust is more of a pigment. This is why a detergent can physically remove some of it from fabric.

Acid let's the rust attach more efficiently.

As an artist you also know that adding acid or something like ammonia (base) to pigments can change the final color. So the rust gets a small chemical change in acid. You can reverse it if you want to turn cotton into paper in the process. Strong bases like concentrated ammonia will "loosen" rust, but also clobber the nice fibers in cotton.

Too many words. Your answer:
Arrest rust's aggressive behavior: try soaking the rust infested cotton in a very diluted ammonia solution. Avoid detergents like Dawn.

Next:
Cut new rust attacks off at the pass: apply tannins to cotton

 

[Hilary Metcalf]

For those who want a link: https://en.wikipedia.org/wiki/Tannin

I am going to reply in a non-scientific way, okay?

Tannins are in the same chemical family as resveratrol, the stuff in cool-climate red wines that is supposed to be healthy. Tannins are more of a nutrient antagonist, aptly called 'antinutrient'. Because they interfere with humans and other organisms getting nutrients from food. You can google the term. IGNORE ads!

Plants make tannins in order to prevent bugs, small animals, fungi, and bacteria from using the plant as a quick lunch. These tannin compounds are active little beasties that glom onto all kinds of other molecules and change them, making them very hard to digest. They bind to cotton, proteins, and a raft of other kinds of molecules and compounds in nature. Tannins love molecules that are nutritionally important to would-be plant munchers, like parasites.

Ever see the dark heartwood in a log? Tannins.

Heartwood has no living plant cells, and so is a target for the heartrot fungus. Nobody home to fight off the bad guys. The tree sends tannins into the Siberia of the tree to block heartrot from even starting.

So. Rust is made of iron and oxygen, and it is called iron oxide. Rust is immune to tannins. But. Tannins already glommed onto the cellulose in cotton, make the cotton immune to further interaction with rust. You can think of it as a battle between squatters. The first one to settle there stops anyone else from settling at that place.

As an artist you get the difference between a dye and a pigment. Dyes attach chemically. You cannot knock them loose easily at all. Pigments are tiny, tiny globs of color, which can attach to a fabric mechanically (or with a binder). Rust is more of a pigment. This is why a detergent can physically remove some of it from fabric.

Acid let's the rust attach more efficiently.

As an artist you also know that adding acid or something like ammonia (base) to pigments can change the final color. So the rust gets a small chemical change in acid. You can reverse it if you want to turn cotton into paper in the process. Strong bases like concentrated ammonia will "loosen" rust, but also clobber the nice fibers in cotton.

Too many words. Your answer:
Arrest rust's aggressive behavior: try soaking the rust infested cotton in a very diluted ammonia solution. Avoid detergents like Dawn.

Next:
Cut new rust attacks off at the pass: apply tannins to cotton

Wow, thank you Jim - finally I have found someone who can talk authoritively, and in terms I can understand - clearly I need to hang out with more scientists and fewer artists! I am very grateful for you taking the time to respond in such detail.

 

[jim mcnamara]

An afterthought:

You know about acid free paper. Archival material, lasts a looooong time. Paper and cotton are made largely of the same stuff - it is called cellulose. If you want your work to persist (how you do this stuff is your decision):

1. Protect it from humidity changes

2. Make sure the final product is as close to neutral acidity as possible. In practical terms, this means neither acid nor base. Hard to do well. Get an archivist to help you. You can fudge it by buying pH strips

pH number is a measure of acidity:
1 acid! ,
7 is neutral,
base is more than 7- more than ~10 turns skin oils into soap, 13 can make paper out of cotton
You want 7. Moisten a corner of the fabric in water, put the test tab on the wet spot, read the color you get and play bathtime with dilute acid or dilute base. Rinse, repeat.

pH strips at Amazon as an example, they run about $US10.00:
https://www.amazon.com/dp/B00Z46VAMW/?tag=pfamazon01-20

 

[Hilary Metcalf]

You know about acid free paper. Archival material, lasts a looooong time. Paper and cotton are made largely of the same stuff - it is called cellulose. If you want your work to persist (how you do this stuff is your decision):

Thanks Jim - I am aware that the process of adding rust to fabric is means it will shorten its life - however that isn't a particular concern to me. It lasts as long as it lasts. I do have a couple of questions arising from your earlier answer:
try soaking the rust infested cotton in a very diluted ammonia solution what do you mean by ‘very diluted’ – 20:1? Can I use cloudy ammonia (which is most readily available at the supermarket), or do I need ‘pure’ ammonia? I am assuming that having soaked the fabric in this solution, I then rinse it to remove any dislodged rust particles, and the ammonia?

Avoid detergents like Dawn. Why?

 

[jim mcnamara]

Household ammonia in any form - the stuff you dilute with water to wash windows. Try about 1/2 teaspoon (maybe a cap full?) in one quart of tap water.
Sneak up on what works for you, starting with the minimalist approach. Too much ammonia will cause the rust to 'wash out'. You can also use swimming pool chemicals instead of stinky ammonia if you have a pool supply place nearby. I just picked ammonia because everybody knows what it is. I hope.

Then rinse one or two times in clear water. Recheck pH when the cotton dries a little. Re-zap in ammonia water if needed.

NOTE: create a "junk" piece of work to mess with. Do not do this with a good piece of work until you figure out a reliable method. Then do not change the method to get rust on in any way, same for the post wash.

 

[jim mcnamara]

Dawn will remove some of pigments or rust from fabric - when used after the rust gets itself attached, of course. I am referring to the "old" Dawn, still out there, not the stuff that is kind to your hands or smells like pumpkin spice (or whatever smell du jour the manufacturer thinks will sell).

 

[Hilary Metcalf]

I am referring to the "old" Dawn, still out there, not the stuff that is kind to your hands or smells like pumpkin spice (or whatever smell du jour the manufacturer thinks will sell).
Thanks - actually I live in Australia, and we don't have that product here. I just assumed you were referring to generic detergent.

 

[jim mcnamara]

Dawn has a detergent, and only a few extra crud "additives". You can buy Alconox if you want - available anywhere - that is almost pure detergent. I would never put my hands in it even when used to wash things. 1 Kg is about $US50.

Google for 'Laboratory detergent' --- Dawn is as close as you can get to that in a supermarket. Does Australia have a preferred supermarket dish detergent that is suitable for making bubble water? - you know, the little ring toy. Small kids, kids (and me) blow on a film of water and detergent, makes bubbles. And we run around trying to catch them. Use that product instead of Dawn.

You can make good homemade laundry detergent (which is ~1% by weight detergent, or less, off the shelf from stores) with:
4 l of warm water
250 ml of washing soda
150 ml of Dawn

So whatever local product does those two things well is how you say "Dawn" down under.