Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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Knifemaker / Craftsman / Service Provider
- Joined
- Aug 20, 2004
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- 37,721
I had a member send me a request for some help and info. As always I suspect there are others who have the same problems, so I will post my email answer to the question on the problem with the clay popping off the blade.
I would also like to make a note that when asking/posting a quire, give all information. The answer is tailored to the specific parameters ,usually.
Quote from reply:
You need to give me more information about the clay, the metal,the blade type, how you will be doing the HT, and how you are putting the clay on.
I will tell you how I do it and maybe that will help.
I use satanite mainly, and APG#36 other times. The satanite works well for detailed hamon, and the APG36 for differential hardening/standard hamon. They are probably interchangeable,though.
I first make a thin mix (about like thin pancake batter) and coat the entire blade. Let it dry, or use a hair dryer or torch to speed it along. When dry, coat with a thicker mix ( somewhere around the thickness of sour cream). If you are looking for a standard hamon, coat the whole blade with about 1/8" to 3/16" of clay - coat it evenly.Use your finger to wipe off the blade edge where you want the martensite to form. Let dry slowly, or use a hair dryer to aid it (I let it dry overnight often, but sometimes gently use a torch when in a hurry). When ready to harden, bring the blade slowly up to about 400F (200C), to make the clay dry and set it hard. Bring the blade up to austenitization temperature and soak for the required time. The clay will be fine at the high temps , if the clay starts out fully dry, it will become almost like ceramic above 1200F (650C).
The main places to look for problems are:
The steel type - shallow hardening, simple alloy - 1060-1095, W1,W2
The clay - any hard drying , high temperature clay - satanite, APG36, fireplace mortar ( not field clay or modeling clay)
The drying - make sure it is fully dry before applying high heat, or it will crack and pop off. If properly dried and fired, it may remain on the blade even after quench. If accelerating the drying ,go slow. You don't want the water in the clay mix to boil, just to evaporate.
The heat source - a forge or oven that can apply even heating. A torch or small forge (one brick) is not usually suitable for clay blades.
The blade surface - it should be CLEANED THOROUGHLY - clean with soap and water and then with Windex. Apply the wash of thin clay and scrub it on with your fingers. The wash layer must be dry completely before applying the main clay coat.
Application - use your fingers for a lot of the work ( It is a caustic mix, so wash right away when done, or wear rubber gloves). A Popsicle stick/tongue depressor works perfect for spreading an even layer. Don't make it too thick. Extra clay will cause problems. As little as 1/16" will make a hamon. 1/8" is fine. 3/16" is plenty.
Drying too fast - Go slow, boiling the water ( in the clay mix) is the number one cause of the clay lifting off the blade.
Hope this helps. Email me with more info or questions if you still need more help.
Stacy
I would also like to make a note that when asking/posting a quire, give all information. The answer is tailored to the specific parameters ,usually.
Quote from reply:
You need to give me more information about the clay, the metal,the blade type, how you will be doing the HT, and how you are putting the clay on.
I will tell you how I do it and maybe that will help.
I use satanite mainly, and APG#36 other times. The satanite works well for detailed hamon, and the APG36 for differential hardening/standard hamon. They are probably interchangeable,though.
I first make a thin mix (about like thin pancake batter) and coat the entire blade. Let it dry, or use a hair dryer or torch to speed it along. When dry, coat with a thicker mix ( somewhere around the thickness of sour cream). If you are looking for a standard hamon, coat the whole blade with about 1/8" to 3/16" of clay - coat it evenly.Use your finger to wipe off the blade edge where you want the martensite to form. Let dry slowly, or use a hair dryer to aid it (I let it dry overnight often, but sometimes gently use a torch when in a hurry). When ready to harden, bring the blade slowly up to about 400F (200C), to make the clay dry and set it hard. Bring the blade up to austenitization temperature and soak for the required time. The clay will be fine at the high temps , if the clay starts out fully dry, it will become almost like ceramic above 1200F (650C).
The main places to look for problems are:
The steel type - shallow hardening, simple alloy - 1060-1095, W1,W2
The clay - any hard drying , high temperature clay - satanite, APG36, fireplace mortar ( not field clay or modeling clay)
The drying - make sure it is fully dry before applying high heat, or it will crack and pop off. If properly dried and fired, it may remain on the blade even after quench. If accelerating the drying ,go slow. You don't want the water in the clay mix to boil, just to evaporate.
The heat source - a forge or oven that can apply even heating. A torch or small forge (one brick) is not usually suitable for clay blades.
The blade surface - it should be CLEANED THOROUGHLY - clean with soap and water and then with Windex. Apply the wash of thin clay and scrub it on with your fingers. The wash layer must be dry completely before applying the main clay coat.
Application - use your fingers for a lot of the work ( It is a caustic mix, so wash right away when done, or wear rubber gloves). A Popsicle stick/tongue depressor works perfect for spreading an even layer. Don't make it too thick. Extra clay will cause problems. As little as 1/16" will make a hamon. 1/8" is fine. 3/16" is plenty.
Drying too fast - Go slow, boiling the water ( in the clay mix) is the number one cause of the clay lifting off the blade.
Hope this helps. Email me with more info or questions if you still need more help.
Stacy
