Heat Treating Recipes

Brazilian Agate: Beautiful swirls of color and bands of light and dark make this a very beautiful stone. Very tough, this stone is tame considerably by heating. Most of this material is found slabbed in 1/4 to 3/8 inch thick. Try 450 degrees to start and work up. I have gone as high as 600 but 550 is generally a good choice to get good glossiness and ease of flaking. Pressure flakes very well with good heating but some color may be lost.

Jaspers: Colors as varied as the rainbow. Usually opaque. Very tough raw but some can be worked. Heat treat slabs starting at 450. Go to 500-550 for some varieties. The "color" rule can come into play. Be careful with the darker colors. Don't exceed 500. Spalls and blanks should start at 400 and generally go no higher than 450.

Novaculite: Most Novaculite is used for billet work and is not slabbed too often. It's real tough on a saw blade. After all, it's used as a whetstone. Spalls and blanks can start at 750. I like 800 for most of the white and porcelain varieties, though some people like 850 or even 900. It gets VERY brittle and glasslike at the higher temperatures.. The purples and reds are a bit more tricky and should start at 750. The black and mixed black and white are even more tricky. Try 600 for Black but don't expect any miracles as this is very hard to heat treat successfully.

Texas Cherts: My favorite flint type because of it's consistency and ease of heat treating. There are quite a few varieties and they all vary with the amount of heat treatment that is best for them. Georgetown:  Blue to Gray, very fine grained. Heat treat slabs at 450-500. Blanks and spalls 400-450. Ft. Hood: Light Gray to Olive Drab, very nice and consistent. Heat treat slabs at 480-550. Blanks and spalls can usually take 500. Some people treat at 425-450 to allow for a tougher stone for percussion. Root Beer: My favorite of my favorites. Root Beer to Coke color, fine, slick and transluscent with some white inclusions at times. Slabs can take 450-500 for a super glossy almost obsidian like quality. Blanks and spalls should go at 400 and usually no higher than 450. Can be tricky and easy to overcook River Cobbles: Tremendous variety of color and texture. Generally small, but high quality. Slabbed material from these can usually take 500-600 degrees. Spalls and blanks can take 500, sometimes a bit more. This is a stone that benefits from hold time. Sometimes the color changes can be dramatic. Pedernales:  Tabs and Pancakes. Nice color from brown to different shades of gray, some with nice banding. Another very high quality chert. Slabs can go to 450-550. Most people who use this material for percussion work like to slightly undercook this stone to retain some resiliency. Try 350-450 for spalls and blanks. Another tricky one, it's best to go slowly and see what works best for you.

Louisiana Pebble Chert: Usually found in fist size or smaller pieces, but high quality. Very tough without heat treating but responds excellently to heat. Most is yellow to tan and is referred to as Citronelle gravel. Slabs of this material can go anywhere from 450-650 degrees, but 550 is my general temperature. Blanks and small spalls can also go to 550. This is another material that responds well to long hold times. Color change can be dramatic, going to orange, red, and purple.

Burlington Chert: Generally white to pinkish with some small fossil and quartz inclusions. Quality varies. Most slabs can take 700. Spalls and blanks treat at 600-650. Color change can be toward pink and red. Some varieties remain grainy no matter how much heat is applied.

Flint Ridge Chert: A favorite of many of the Northern Knappers, the colors seem to be endless as well as the quality. Some quartz inclusions and a lot of cracking in some pieces. Slabs can easily take 650 in my experience. Spalls and blanks for percussion can go 600-650. Grainier types can probably take a little more heat, probably 675-700.

Western Agates: Beautiful material in a wide variety of colors. Turns very glossy and waxylike after proper heating and gets brittle. Most is slabbed and used for pressure work. Try 400 to start and then possibly go to 500. Can be very tricky and fragilel

Mook Jasper: From Australia, also called Mook or Mookaite. Tremendous variety in color and quality. Most is basically red with different colors inclusive. The white, chalky types or areas do not seem to take heating well. Most is slabbed as it is very expensive. Try 500 for the darker material and 550 for the lighter colored. Turns almost plastic like in appearance. A current favorite with many knappers wishing to make beautiful, gem quality points.

Agatized Coral: From Florida. Light Gray to white. Absorbs cuttting oil and changes color. Be sure to wash well. Most is slabbed as it is expensive. Try 600-675 for most slabs, but I have gone to 700 with good results. Some color change can take place.

Alibates Flint: Beautiful material. Some red with white streaks is predominant. Some varieties are blue with various color streaking and banding. This material is getting hard to come by. Very tricky to heat treat. Slabs can go to 500 or even 550. Spalls and blanks can go 400 to start and sometime 450-500, depending on size and thickness.

Flint River Chert: From Georgia. Very beautiful, butterscotch or honey colored. Transluscent when held to the light. Very fine material when not filled with ash pockets. Slabs can take 550. Spalls and blanks start at 450 and can sometimes go to 500.

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