Sand vs Oil for Tempering

[Will W. 94]

Its recommended quite often for a cheap and low tech setup to use a toaster oven and a pan of sand for tempering, and its a good system, one i utilize myself. 

However, i have seen many use a hot oil setup for tempering as well, maintaining their desired temp on the oil with the blade submerged. 

My curiosity causes me to wonder, would it be beneficial to use oil instead of sand to even out the temperature swings in a cheap oven? Or would it simply achieve the same end result?

I would imagine the sand, being a solid, would hold onto temperature better then a liquid, thus stabilizing the temperature more efficiently, but im still curious what everyone thinks. 

[Kreg Whitehead 39]

Why would either be preferred over an oven/air?? I can see faster...just not better.

Edited December 12, 2018 by Kreg

[Jerrod Miller 283]

You're just going for (thermal) mass, so what the material is doesn't really matter.  Sand is a lot nicer to have in your oven than many oils though, because it isn't going to smoke or burst into flames.  

For those reading this not familiar with the intent:  Food ovens are not all that tightly controlled and just maintain an average temperature (which may or may not be close to what the setting is indicating).  It will over-shoot that temp and then let it fall a bit below that temp.  Swings of 20+ degrees F above and below the set point are not unrealistic.  Having thermal mass in the oven resists the quicker changes up and down, thus holding the average temp more constantly than the air in the oven.  Sand and oils, or anything else that flows over or conforms to the blade shape, helps in that it is easy to "bury" the blade into the thermal mass, thus fully utilizing it.  

[Will W. 94]

Thank you for the clarification, Jerrod, i should have mentioned the intent of using either to better regulate temperature. 

My thought was to use a high flash point cooking oil, peanut oil for instance, instead of something nasty like motor oil. 

It would be interesting to run a series of tests to see which, sand or oil, will maintain a more average temperature.

Whichever one is better, i would imagine it would only be in the ballpark of a few degrees less fluctuation, and probably would have no practical effect on the temper of the blade.

[Vern Wimmer 468]

stabilized? On a blind "don'tknowadamnthingaboutchemistry"" POV I would wonder if there wouldnt possibly be an issue of some non-flammaboe evaporation of some chemicals in a petrochemical oil that might , just by a teeny fraction, make it less desirable than sand for constant temp. Just a wild thought.

[Jerrod Miller 283]

Much like forge design, even more so really, this should not be overthought... 

[Will W. 94]

Oh, come on, overthinking and undershooting are my specialties! 

[Gerhard Gerber 157]

OK.....this just brings up more questions......I was fully planning on building an oil tank for tempering some day......as soon as I figure out where to get the necessary electronics....

Blame watching Man at Arms videos for that.....

So, good to see it's maybe not necessary.

Since getting a cheap multimeter with thermometer I've learned my bachelor tempering oven was about 20C higher than indicated, and the tray full of sand really evens out the temperature something amazing...

I do 2 x 1-hour temper cycles, and I flip the blade over between cycles.

My question is which would be better:

-edge in the sand

-spine in the sand

-whole blade burred in the sand......? 

[Jerrod Miller 283]

51 minutes ago, Gerhard said:

-whole blade burred in the sand

This.  

[Doug Lester 156]

What are you thinking about as far as a container for the oil bath goes?  Something like a counter top roaster?  I've thought about it too from time to time.  Because you would be pushing the oil  up to near the flash point I would only do the tempering in the roaster outside of the house and the forge with a dry chemical fire extinguisher and the roaster lid close at hand.  Don't even think of having the water hose handy in case of fire.  You might even be able to use the set up for marquenching (done it-don't recommend it) but from what Kevin Cashen told me that requires a specialized oil to get the rate of cooling that is needed at those temperatures.

Doug

Edited December 13, 2018 by Doug Lester

[Joël Mercier 307]

A 20$ Chinese PID and solid state relay can turn a 30$ toaster oven into a precise tempering device. 

[Jerrod Miller 283]

Also just going to throw this out there for you all to look up if you want:  Low temp salt baths.  

[Doug Lester 156]

Didn't think about that, Jerrod.  Do you think that the low temperature salts would melt in an electric roaster?  It would reduce the fire risk but you would have to guard against  any water getting near the bath.

Doug

[Jerrod Miller 283]

I wish I could say it was my idea, but just something I recall others chatting about years ago on this forum.  I know you can customize your salt blends to get all kinds of melt points.  

I mean, if it was good enough for Don Fogg...