A simple trick is to put the piece you're annealing on a thick chunk of steel heated to the same temperature, and put the whole mess in the annealing medium.  The large mass greatly increases the amount heat that must escape to reduce the temperature by a given amount.  If you have a piece of thick-wall tubing, that should work even better.

1 hour ago, The Forest Ninja said:

I've made camping fires on sandy beaches many times and never saw any glass formation. For annealing, I was thinking a lot smaller of a fire.

But your fires weren't getting that hot most likely.  What Frosty was saying is that you stick a blade in there at 1400 and it will glass the sand onto its surface.  Or that's how I understood it anyhow.

14 minutes ago, Mike BR said:

A simple trick is to put the piece you're annealing on a thick chunk of steel heated to the same temperature, and put the whole mess in the annealing medium.  The large mass greatly increases the amount heat that must escape to reduce the temperature by a given amount.  If you have a piece of thick-wall tubing, that should work even better.

Thick wall tubing... There's an idea!  If it's a flat piece, though, what's "thick"? 3/4"? 1"? 2"? Thicker the better I assume...

Sure, that's why silica sand can be used as a flux. It's melty at about 1700, 1800 degrees F. Not my favorite though. Or dirt dauber nests if you want to really go old hillbilly smith style. 

I think the helper piece of steel is probably the way to go. Enough mass, and you can get away with a lot of things that insulate - vermiculite, clay, my preference is wood ash. It's cheap, works well, and is easy to store, just don't get it wet. And if you do, it's easy to replace.

2 hours ago, The Forest Ninja said:

Has anyone ever annealed steel buried in a few inches in sand

Welcome from the Ozark Mountains.

I have had good results using woodstove/fireplace ashes.

I can't control the wind, all I can do is adjust my sail’s.~ Semper Paratus

 

I have a piece about maybe 1" X 4" X 6" that I use.  But I stick to some pretty basic alloys, and generally anneal by leaving the piece in my gas forge, shutting it down, and blocking the vents.  I put small pieces on the castable floor of the forge, with the hot chunk of steel on top.

Building a fire on top of the material you wish to anneal in whatever  soil, clay, sand, etc. Heats just the material above the piece so it cools more on one side than the other which might promote warping.

However if you were to use a steel box filled with sand, lime, etc. and build a fire all around it would slow cooling more evenly. 

It may seem that laying your piece on another bar of heated steel would promote uneven chilling but steel is a good enough conductor of heat both piece and . . . Oh heck I can't think of the term, call it a thermal battery. Anyway the heat given by the battery will remain equal through your piece. 

If you want to put thermal batteries on both sides of the piece a little fire clay, perlite, etc. between them is just fine. An excellent clay to use for HOT work like this is Bentonite, it's vitrification temp is well above what most propane forges max out at. 

Putting your piece in a piece of heavy pipe is using a "muffle", being the pipe. It muffles temp changes by adding thermal mass to the piece. I've headed 3,000f heavy fire brick to add thermal mass to the piece by sandwiching it between the brick and leaving it in the hot forge. With both ends closed tight and a wad of kaowool closing the burners it anneals pretty nicely. 

More properly nicely enough for me but I am NOT a bladesmith guy though occasionally I needed to harden and temper tools, like the little pry bar I made specifically for fossil hunting. It was very similar to a "speed bar" used by frame carpenters but it was smaller and thinner so I could drive it gently between layers of stone without damaging fossils. 

Frosty The Lucky.

8 hours ago, Frosty said:

Oh heck I can't think of the term, call it a thermal battery

Heat sink?

Not the one I was thinking of but a lot better than thermal battery. 

Frosty The Lucky.

Thermal mass?

Thermal mass is a much better term here. Not sure why I couldn’t pull it out of my memory…

Yeah, thermal mass is a better term, I believe I deleted it when I edited my above post, convinced there was a better term. 

I know Goods, I have a brain full of useful terms, tricks, techniques and just stuff but it's getting harder and harder to convince them to stop hiding in the wrinkles in my brain. Some times the voices will rescue me though.

Frosty The Lucky.

Good Morning,

I use a large container of Garden Lime, for annealling. It is not toxic and it is easy to find. I learned from John Adolph to use Garden Lime for flux when welding. It doesn't eat up the Fire Bricks.

Neil

If the piece does warp in the anneal, it shouldn’t be too hard to straighten (see what I did there?)