do yall change/filter quench oil--if so, how often??

[timfish]

I use canola in an old ammo can--how often do yall recommend filtering/changing it out--how many knives---I know this is a weird question--but I was just wondering if Canola (or Parks 50)goes bad--please and thankyou!!!

 

[Joshua Fisher]

Canola starts to change the moment you start using it. I typically recommend to beginners to change out canola oil every 6-8 months depending on use. Speaking with the people that distribute parks 50 it should last for years if stored and used properly (don’t edge quench and burn your oil) hopefully someone can chime in with more details on oil life.

 

[Bill DeShivs]

I have been using the same gallon of canola oil for 20 years. I mostly quench small pieces like springs, but every once in a while I do make a knife.
It still seems to work fine. It has quenched thousands of leaf springs.

 

[Stacy E. Apelt - Bladesmith]

Canola is a low acid vegetable oil. If exposed to moisture or air exposure it will eventually go rancid but should be fine for a long time if stored properly. I would say replace it every year under normal knife shop use.

Parks is a mineral oil base product and very stable. It should last many years. I have a large quench tank of parks 50 that is a good 20 years old and works just fine. If you tore it in a closed drum, it should last almost forever.

Straining through a screen filter at least yearly is wise, especially if you do clay quenched blades. Avoid getting water or leaves into the oil tank if it is stored outside. It should always be covered fairly tightly to keep critters and stuff from getting in the oil.

For those interested in the chemistry of oil going bad:
The enemy of oil is heat, air, and water.
Heat breaks the oil down fairly rapidly, so avoid high heat and quenches that "burn" the oil. The heat mainly speeds up oxidation, ... read on.
Air and water both contain oxygen which causes oxidation of the oil. The carbon-carbon bond in oils can be broken by oxygen. The oxygen makes new chemicals like aldehyde and carboxyl compounds, which form fatty acids, and those compounds go rancid. As I just noted, the higher the temperature of the oil, the faster the oxidation occurs. At the temperature of a quenchant, around 130°F/55°C, the oxidation is slow. In a deep fryer at 350-450°F/175-230°C, the degradation is pretty fast, and the oil may only last a week to a month. One way to slow the degradation is to limit the surface area exposed to the oxygen. A tall thin quench tank has a smaller surface area than a wide pan. A tightly closed tank or container does the same.

 

[Domburger]

Use to quench my steel in canola oil for several years in a row without filter or cleaning or so. That worked fine, but in the long run it got rancid. Five years ago I bought 10 l. of Durixol W25 oil and it makes my life easier because it cools much quicker, it doesn't vaporise and is thermochemical stabile. It should last almost forever. I storage it in an air- and watertight metal ammo box.

 

[timfish]

Many thanks for all the great info,,,