Carbon steel maintenance: 70% isopropyl vs. 91% isopropyl vs. Windex

[AFAustin]

My knives are mainly trad folders, a mixture of carbon and stainless. When I first came down with this illness and began looking here for the best way to ward of rust/corrosion, especially on the carbon blades, I liked David (OWE)'s advice to use isopropyl (rubbing) alcohol or Windex. I went with the rubbing alcohol in the more common (and slightly cheaper) 70% concentration. Frankly, it's worked well and a quick wipe with it before putting away a folder has done a good job of keeping my knives rust free.

I've read that some recommend the stronger 91% variety for this purpose, and David has said that he actually uses Windex. I bought some 91% to try but confess it doesn't appear to evaporate more quickly---that my old eyes can see anyway---than the 70%.

I haven't really experimented with Windex but am wondering if the ammonia is any problem if you later use a knife wiped down with it for food prep. I'm guessing the ammonia evaporates away, but then I had problems with high school chemistry.

So the upshot of this post is, for those who use any of the 3 (70% iso., 91% iso., or Windex)---which one, and why?

Thanks,

Andrew

 

[Obsessed with Edges]

I've used all three pretty much interchangably, just depending on what's handy; most of the time, it's Windex. Haven't had any issues with any of them. No issues with too-slow or inadequate evaporation either, with any of them (and I used these in the Austin, TX area for 20+ years as well, while I lived there). On a knife blade, it's easy to see these evaporate off the blade, and it's pretty obvious when it's dry; I've never seen any of them linger on a blade longer than maybe 30 seconds or so.

I wouldn't worry about the ammonia in the Windex. My impression is that the ammonia is pretty low concentration and evaporates off very fast. I think Windex is mostly water anyway; water is the first-listed ingredient on the label, with 'cleaning agents' listed secondarily (doesn't show ammonia specifically, at all). Even when I've gotten it on my hands, it's relatively easy on the skin, so I don't think the ammonia is very strong in it (isopropyl alcohol is more drying on the skin, for me). At any rate, Windex is what I've used to wipe down my folding knife blades after cutting fruit or other foods, and I've not had any issues with residue left on blades, of which there never seems to be any there.


David

 

[AFAustin]

Thanks, David. Your advice is always much appreciated. :thumbup:

Andrew

 

[Obsessed with Edges]

You're welcome, Andrew. :thumbup:

BTW, I do keep a bottle of 91% IPA on my bathroom countertop. I use it to flush moisture out of my folding knives after I've given them a dish soap & water bath. I rinse with hot tap water (~120°F or so), then douse the entire knife with the 91% IPA, letting it run into & through every nook & cranny. Does a very effective job of drying everything out. I'd specifically AVOID doing this with any cellidor-handled Victorinox SAK, however; the cellidor is too sensitive to IPA, and it'll soften and/or warp after being wetted by it (learned this the hard way). With those, the dish soap & water bath with a hot tap water rinse is good enough (it's stainless, so there's not much to worry about anyway).


David

 

[Rey HRH]

The 70% difference is that it's more effective in killing bacteria than 90% IPA. But for evaporation or making sure you take away any moisture, the 90% would be better because there's less water in it to begin with.

But my question is: while you've removed the water from the blade, I think you're just keeping the surface exposed to the moisture in the air, i.e. humidity. Making the blade still subject to oxidation. So I would think that you would still / should apply a barrier between the blade and the atmosphere such as some non-evaporating oil. I think this is the same principle why gun barrels have a film of oil applied before storing. If you decide to leave the blade with no barrier protection, then you'd also have to make sure you don't touch the blade afterwards with your bare fingers as I believe your fingertips can also leave some acid (which promotes rusting) along with body oils.

A better evaporator is acetone as that is what's used in cleaning precision glass lenses. It would be fine with metal but I don't know how it would be with the various non-metal parts of the knife. It would definitely eat some plastic types.

 

[AFAustin]

David, good to know of that particular use for the 91% IPA. After washing and rinsing, do you see a need to dry with a hair dryer or some such before applying the 91% IPA?

Andrew

 

[Obsessed with Edges]

David, good to know of that particular use for the 91% IPA. After washing and rinsing, do you see a need to dry with a hair dryer or some such before applying the 91% IPA?

Andrew

I've never used a dryer (hair, heat gun, etc) before applying the IPA. If I've rinsed in fairly hot water, most of that evaporates off pretty fast anyway, because the knife gets nicely warmed up in the hot rinse. Once I've doused the knife in IPA, any residual moisture is gone. Alcohol works a lot like WD-40 is reputed to, in the sense that it 'displaces' water and carries it away. I used to work in the electronics/semiconductor industry, both in the military and in the private sector, and IPA is what's generally recommended to flush water out of electronic gear that's gotten wet for whatever reason. This is why I became a believer in it, for thoroughly flushing water out. It works.


David

 

[Bill DeShivs]

Windex, ammonia, alcohol, etc. only clean the blade. They offer no rust protection at all. In theory, they can promote rust by removing any trace of oil from the blade.
A quick wipe with WD 40 is much more effective. When it dries, it leaves a thin film of mineral oil on the steel.
WD 40 will also displace any water when liberally sprayed on a knife, and I have found no handle material that it harms (it should be wiped off of stag.) WD 40 has the added advantage of lubricating the moving parts.

 

[Obsessed with Edges]

I'll also agree, with carbon steel blades/knives, a little bit of oil after cleaning up is good practice and common sense. I have used WD-40 occasionally for flushing out very dirty or rusty knives, usually before I wash them in dish soap & water. Once I've washed them though, I've come to prefer using the IPA to flush remaining moisture out, then use a little oil targeted to specific areas of the knife, mostly in the pivots. I usually don't even oil my blades anymore, as simply keeping them clean & dry (with the Windex) takes care of about 99% of corrosion worries, for me.


David

 

[AFAustin]

You're welcome, Andrew. :thumbup:

BTW, I do keep a bottle of 91% IPA on my bathroom countertop. I use it to flush moisture out of my folding knives after I've given them a dish soap & water bath. I rinse with hot tap water (~120°F or so) , then douse the entire knife with the 91% IPA, letting it run into & through every nook & cranny. Does a very effective job of drying everything out. I'd specifically AVOID doing this with any cellidor-handled Victorinox SAK, however; the cellidor is too sensitive to IPA, and it'll soften and/or warp after being wetted by it (learned this the hard way). With those, the dish soap & water bath with a hot tap water rinse is good enough (it's stainless, so there's not much to worry about anyway).


David

After my wash & rinses, the water doesn't evaporate very fast and so I've used a little craft dryer my wife loans me. I got curious and just checked the temperature on the "hot" water from our utility sink---105 degrees F. Guess that's why I need a dryer!

Andrew

 

[Obsessed with Edges]

After my wash & rinses, the water doesn't evaporate very fast and so I've used a little craft dryer my wife loans me. I got curious and just checked the temperature on the "hot" water from our utility sink---105 degrees F. Guess that's why I need a dryer!

Andrew

Makes sense.

I got accustomed to using 120°F water after fighting some water heater thermostat issues while I was living down there in the Austin area. In doing that, I learned that 120°F temp is pretty much standard for 'safe' hot water, according to code, I believe. It's hot enough to be useful without being dangerous (scalding hot), and I think it's also the 'default' set temperature for new water heater thermostats. Since fighting those issues and having to replace a couple of defective thermostats, I tend to be disappointed if 'hot' water at the tap isn't pretty close to that mark. And thankfully, the thermostats are adjustable to get it there, assuming they're working properly.


David

 

[Bill DeShivs]

WD 40 puts a light coat of oil where you CAN'T see it-all those nooks, joints and crannies.
I have seen the rusted guts of enough knives that I know they need protection inside-as well as out.

 

[David Martin]

Seems like I've read somewhere that mark (120*)was the default. My knives of 01 will tarnish/ turn black and discolor if I don't wash them right after use, dry and apply a coat of mineral oil. WD-40 works too. Just wipe lightly and allow the oil to remain on the blade. And these will turn purple heart wood dark as walnut. Plus, if you live in a humid area use more care. DM

 

[kelbro]

Wow. What are you guys doing to get your knives dirty enough to need washing?

 

[AFAustin]

Wow. What are you guys doing to get your knives dirty enough to need washing?

For me, a wash most often happens when I first take a knife in---especially if it's used or else new but has sat around for a while and there's some dirt/gunk in the joints.

Andrew

 

[Obsessed with Edges]

Wow. What are you guys doing to get your knives dirty enough to need washing?

As with Andrew, usually when I get a 'new' (to me) old knife, which often needs a thorough cleaning. Lots and lots of old knives out there with sticky, gummy, gritty stuff in the pivots and in the gaps between the springs & liners. I've washed old knives purchased on the 'bay that reeked of cigarette smoke. I've also washed knives that were heavily rusted, after flushing them out and scrubbing with WD-40. And occasionally, after cutting fruit with folding knives, the juice will get into the joints and becomes very sticky; so, a good dish soap & water bath is usually the best way to clean that up. Also for cleaning folding knives that get accidentally dropped in the dirt on occasion.


David

 

[David Martin]

This is funny... Now, you boys don't be cutting anything with them knives. Just look at em. DM

 

[AFAustin]

As with Andrew, usually when I get a 'new' (to me) old knife, which often needs a thorough cleaning. Lots and lots of old knives out there with sticky, gummy, gritty stuff in the pivots and in the gaps between the springs & liners. I've washed old knives purchased on the 'bay that reeked of cigarette smoke. I've also washed knives that were heavily rusted, after flushing them out and scrubbing with WD-40. And occasionally, after cutting fruit with folding knives, the juice will get into the joints and becomes very sticky; so, a good dish soap & water bath is usually the best way to clean that up. Also for cleaning folding knives that get accidentally dropped in the dirt on occasion.


David

It is amazing what a little TLC can do for a knife that's been neglected. Spending a few minutes on a good wash, scrub, and rinse, along with some Flitz or Mother's Mag applied with a little elbow grease, can turn a dull and sad looking traditional folder with a gummy joint into a small shiny jewel with a slick and satisfying action. Very nice indeed....

Andrew

 

[kelbro]

That makes sense. Never thought about buying used knives off the bay. I do rinse mine off when cutting oranges or other sticky sugary fruit.

 

[jpm2]

This is funny... Now, you boys don't be cutting anything with them knives. Just look at em. DM

You got to remember we are in the extreme knife using minority.
My knife gets stuff in it most people have never heard of. Not only stuff that looks dirty, but will eat your flesh in time.