How long does canola oil last?

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elementfe

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I'm wondering if anyone has an experience/experiment supported guideline for this.

I've been using canola for some years for a couple reasons, the main one being that I imagine that it's somewhat less toxic than petroleum oils (or maybe toxic in a different way 🙄)
There's often a caveat when experienced bladesmiths (L. Thomas, Cashen) mention canola- that it becomes unpredictable and breaks down over time.
My question, is there any kind of guideline other than guesses, as to when to replace it?
I'm asking y'all to do my homework for me, it's true, but as in so many cases, it's likely someone already has, and I just don't know where to find the results.
Thanks!
 
Canola is not a good quench oil. Throw it away and buy some Parks 50.

Yeah, it’s probably less toxic, yeah, it’s cheap and available but it will not result in a properly quenched blade. Larrin’s research on this was very surprising.

Hoss
 
DevinT said:
Canola is not a good quench oil. Throw it away and buy some Parks 50.

Yeah, it’s probably less toxic, yeah, it’s cheap and available but it will not result in a properly quenched blade. Larrin’s research on this was very surprising.

Hoss
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Thanks, as always, your view is the one I'll take to heart- is Larrin's research in his Knife Engineering book, or where might I find it?
 
It's hard to say how long, because the breakdown will be a combination of oxygen exposure over time and break down from heat. Like for frying at home you usually only want to use it two or three times, but that's different in a chip shop.
So depends on what you're doing?

I agree with the concerns about quench oils being a petrochemical product. You're probably using more gas and petrol, but still we should minimise all that. For this reason I've been using Aquaquench 251 for a bit, it's a concentrate you mix with water to slow down the quench speed of the water. It appears to be significantly more environmentally friendly than a quench oil, and is also more versitile as you can adjust the concentration to get different speeds. I've gone for a bit faster than parks 50.
I've been happy with the results with 26c3 steel, but i don't have the equipment or inclination to do a formal research paper on it (do have the skills, if someone wants to equip and motivate me 🤑)

Looking at the MDS for Parks 50 quench it doesn't appear to be unusually toxic for that sort of product. Don't drink it, maybe wear gloves and definitely wear eye protection

Larrin's research on this is also on his Knife Steel Nerds blog

edit: it's also worth considering that you will have to ask this for any quenchent. If you use water various salts will build up and adjust the quench behaviour somehow, although i don't know if it will make a perceptible difference.
 
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Thanks everyone.
Larrin's article (blog with youtube) actually indicates that canola performed pretty well in his tests with 52100.
The results with 1084 are disturbing, and though I'm taking them seriously they don't match the results I've been getting- I've used canola on a number of smaller stock removal knives, and they show good edge retention, though I'm well aware that the goal of "fully hardening" may not be met.

Larrin also demonstrated that a freezer treatment with AEB-L can make a darn good knife, (though not the ultimate knife) which is contrary to all the dogma currently preached.
I find this craft to be a constant balance between real world and theory- do I spend twice the time chasing that last 3%? On some knives absolutely, on some no way.
 
I have used the same gallon of canola oil for 18 years (with a little added to make up loss) to quench 1095 switchblade leaf springs.
I realize these leaf springs are much smaller than knife blades, but I have done literally thousands of them -one at a time, plus some backsprings.
I think I have had half a dozen break over the years, and they were all made from the same bad piece of steel.
Not very scientific, but those are true results.
 
I don't have as many years as Bill but I haven't changed out the canola oil I use for 1095 either. The only blade that has broken is one that I intentionally broke to see the grain structure, which seemed fine.

I keep the oil in a paint can that I seal up as soon as the oil cools so I think the effects of oxygen are somewhat minimized. I've never done a true hardness test either so who knows.

This thread has convinced me to try some Parks 50 though....the canola oil was cheap but I'm making more and more knives so probably time to up my game.
 
Learn all you can about heat treating. Buy and use the best equipment. Do a lot of testing.

HT is often a neglected part of knife making. Figure it out and you’ll gain a lot of confidence in your work.

Good heat treating is worth it.

Hoss
 
Bill DeShivs said:
switchblade leaf springs.. . . plus some backsprings.
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I'm not trying to start an argument, Bill, but IIRC, you specialize in folders, so how thick and big is the spring stock you're quenching?
The reason I ask is because really thin stock can air harden, even if it's not an air hardening steel because the key is cooling the steel quick enough, and thin stuff cools really quick. So the canola oil might just be cooling it down to grab it, not quench?
 
If you’re making knives to sell, I recommend using the correct quenchant. When I first started out I wanted to make the best knife I possibly could, but I still used canola oil because I thought Parks 50 or even AAA were overpriced. However, after reading Larrins research on Knife Steel Nerds, I realized that using the correct quenchant takes the guesswork out of the equation. I ended up ordering some Parks 50 and it is well worth every penny.
 
I'm not suggesting anyone use canola oil, nor am I suggesting it doesn't go bad.
Just giving my experience. I do keep it covered.
 
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TheEdge01 said:
If you’re making knives to sell, I recommend using the correct quenchant.
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The problem is that the correct quenchant is a more complex decision than just what a ball cooling test shows. Canola is grown and processed around here and is biodegradable, Parks 50 has to be shipped and is made from petrochemicals.
As someone who mostly makes kitchen knives if can get a steel that hardens acceptably in canola then there are a bunch of other reasons to use it over say parks 50
You can't get fixated on just one data point, you have to consider the whole process.
Parks 50 is a good option, especially if you just want a simple solution, but the quenchant you use is just one component of a complex system
 
Alex Topfer said:
The problem is that the correct quenchant is a more complex decision than just what a ball cooling test shows. Canola is grown and processed around here and is biodegradable, Parks 50 has to be shipped and is made from petrochemicals.
As someone who mostly makes kitchen knives if can get a steel that hardens acceptably in canola then there are a bunch of other reasons to use it over say parks 50
You can't get fixated on just one data point, you have to consider the whole process.
Parks 50 is a good option, especially if you just want a simple solution, but the quenchant you use is just one component of a complex system
Click to expand...
I see what you’re saying. If it works for you, then go for it. Personally, I’d rather use a quenchant that is specifically designed for knife making.
 
Alex Topfer said:
You can't get fixated on just one data point, you have to consider the whole process.
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This is the key, I believe. Larrin (and possibly those who have read his book more than once), would be better than me to go here, but I'll give it a go:
The most important data point(s) in the quench process is the graph that shows the "nose" of the curve (I can't remember if it's the TTT curve or something else). What this curve shows is the temp of the steel on the Y-axis and time on the X-axis. It also shows the areas of the curve where the different phases(?) of steel are (pearlite, austentie, martensite, banite, etc). And in my understanding, as long as you reach your final temp at a time in the austentite(?) area (best to avoid the nose all together), you will harden your steel.
The specific quenchants will give you the data to draw your own time/temp line, but these are specific to a certain size of steel, usually in thicker cross sections than what we knifemakers use. What this means practically is that because thinner steels cool faster, the cooling rate curve you get from the manufacturer specs needs to shift to the left to be accurate for the thinner and smaller cross sections knifemakers use. Which is my understanding why (depending on how thin the final grind is before hardening) our1084/15N20 damascus chefs blades can air harden.
So, I think part of what Alex is saying is that whatever quenchant that gets the cross-section of your steel hard in the proper amount of time is the correct quenchant for that cross section of that steel.
 
Getting good hardness with canola on the 52100 reflects the good hardenability of 52100. Picking out that datapoint to say that canola is good doesn’t make much sense. When you get full hardness in air with a stainless you don’t say that air is a good quenchant.
 
Larrin said:
Getting good hardness with canola on the 52100 reflects the good hardenability of 52100. Picking out that datapoint to say that canola is good doesn’t make much sense. When you get full hardness in air with a stainless you don’t say that air is a good quenchant.
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But if you get good hardness for a specific part using canola, can't you say that canola is a good quenchant for any part that meets the same physical parameters (dimensions and type of steel)?
 
weo said:
But if you get good hardness for a specific part using canola, can't you say that canola is a good quenchant for any part that meets the same physical parameters (dimensions and type of steel)?
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If your plan is to only use steels as hardenable as 52100, yes. Just like if you are heat treating air hardening steels you can use plate quenching.
 
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