Superquench formula for the UK ?

  • 5 Gallons of water in a bucket that has a lid that seals well. - UK version - water
  • 5 pounds of salt (these three containers came up 2oz short, the mix still works just fine.) - UK version rock salt or ice cream salt
  • A bottle of dishwasher rinse-agent. (Jet-Dry works too, in the original recipe it was Shaklee Basic #1) - UK version - Finish or Home Stuff drying agent
  • A bottle of Blue Dawn Dish Detergent (the blue dye turns green when the mixture finally wears out a few years from now, other colors don't help in this way.) - UK version Dawn or Fairy
 
What am I missing here? Is there any purpose for this? It seems it's a oversaturated brine with soap in it. Salt will stick and slow down the quench. Soap will make it clean :/ Isn't medium speed oil better?
 
It's purpse, as I understand it, is to be an extremely fast quench. Faster than plain water, with the salt breaking up the vapor jacket. It is intended for steels that have super low hardenability, or steels that have been thermal cycled to such an extreme that a fast oil quench or plain water isn't fast enough. I really don't undedrstand the purpose of the jet dry and dish detergent, except to help break up water tension to get better contact on the knife? To make the superquench even faster than a brine solution? Not really sure about the detergent/jet dry, but I think that's it.
 
Don't take the following as my recommendations. I don't see the need for exotic quenchants in modern knifemaking.

The jet dry is a wetting agent and lowers the surface tension ... thus helping collapse the vapor jacket. The soap does the same. The salt makes a brine solution for a fast quench speed. I agree that there is nearly twice the needed salt in the popular formula.

Superquench was created by a Sandia labs as an alternative to lye quenchants which were dangerous. It is aimed at hardening low carbon and mild steels.
I personally don't see any need for it in knives, but there are a few folks who use it.

The original recipe is:
5gal. water
5 lbs. table salt
32 oz. dawn dish soap (blue)
8 oz. Shaklee basic I (I don't think Shaklee makes this anymore. It is a dishwasher drying agent same as Jet Dry)

There was another odd quenchant a while back called GOOP. It was supposedly created by Wayne Goddard and often referred to as Goddard's Goop. Mark Williams used it, too.
It was a concoction of machine gun oil, bear fat, bacon drippings, dish soap, and many other oddities. Some recipes had lye in it.

Another GOOP recipe was:
40% Crisco or other vegetable shortening
40% paraffin oil or mineral oil
20% ATF
 
The Jet Dry and dish soap are surfactants. They act to lower the surface tension of the bubbles, allowing the salt crystals to break the bubbles readily and thereby reduce the vapor jacket significantly.
Prepare to sacrifice a lot of high carbon steel to the quench gods. A railroad spike knife will get its hardest with this stuff. 1095 and the like, make two blades to get one intact if you're lucky.
 
Recently bought 6m of 1060. I needed only 30cm but the price was so good and they didn't want to cut it off. 15€ for 6m :D...play time..
I'll make two knives and check the difference between brine and superquench. I'll grain refine to make the hardening line in brine cca 10mm of the edge and compare to superquench. If superquench is faster, the line will move up.
I have some suspicions already. All water quenches are vigorous so the vapor blanket has low significance. Killing bubbles is irrelevant. Slowing formation of bubbles is relevant. Can that soapy things add to salt, we'll see. If it does, good. That means I could finally quench too refined 1060. :)
Edit: If it works, then there is a chance to break my Ti record of 66HRC. 67HRC sounds better. 68??? :eek:
Edit2: Love this forum :)
 
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JoeBusic said:
Is there any purpose for this?
Click to expand...
The surfactants prevent the vapor jacket from forming, and this allows for rapid cooling of the surface, basically work hardening mild steels making them good for blacksmithing tooling. I can't remember where I wrote this down from but here's some old notes:
"Liquid quenches go through 3-phases of heat removal: vapor, boiling and convection. Vapor is the first and slowest heat transfer because of the insulating steam jacket. After cooling to below where the vapor jacket forms, liquids boil and this heats/cools the surface unevenly because of the tiny bubbles that form. Below the boiling point liquids are in constant contact with the surface and quick and even cooling occurs from this point on. Superquench works to minimize the vapor and boiling phases of cooling."
 
Someone made a paper about it. Observe:

Quenching mediums Cooling rate compared to water

Heavy brine +Surfactant ..................> 1.96 (approx.)
Heavy brine (15% Salt) ......................> 1.96 (approx.)
Sodium hydroxide (10%) ..................2.06 (Chandler, 1996)
Brine (10% Salt) ....................................1.96 (Chandler, 1996)
Brine (7% Salt) ......................................1.00-1.96 (approx.)
Water (Tap water) ...............................1.00
Lube oil ..................................................0.20 (approx.)
 
Stacy E. Apelt - Bladesmith said:
There was another odd quenchant a while back called GOOP. It was supposedly created by Wayne Goddard and often referred to as Goddard's Goop. Mark Williams used it, too.
It was a concoction of machine gun oil, bear fat, bacon drippings, dish soap, and many other oddities. Some recipes had lye in it.
Click to expand...
I can't say that Wayne created it but likely did. I read one of his books a few months ago and he descibes it. It's purpose was edge quenching rather than the entire blade. The idea made sense to me, similar to a clay hamon, at least similar results. A hardened edge with a more flexible spine is the idea, as I understand it. When I asked about edge quenching in this forum it was not recommended, so I haven't.
 
Thanks for that chart, Joe. It shows the relationship that salt content has as well as the increase by adding surfactants.

Nerd talk:
The temperature needed to boil a solution of salt in water will increase about 0.5 C for every 58 grams of dissolved salt per kilogram of water. - Raising the boiling point starts the liquid phase of the quench sooner. 5# salt is 2.26Kg. 5 gallons of water is 18.9Kg. Thus, the boiling point would be raised to 216°F/102°C. This will slightly speed transition from gas phase to the boiling phase of the quench, which speeds the transition to liquid phase.

Saturation at the boiling point of salt in water is 28% - Superquench is a 12% solution of salt (technically a bit less since the soap and jet dry are part water) Normal quenching brine is 7% to 9%, seawater is around 3.5%. The additional salt increases the solution percentage at the boiling/vapor point.

The thermal solution curve for max salt concentration in water meets at 58°C/135°F - That would imply that 50-55°C/120-130°F would be the best temperature for Surpequench.

Surfactants decrease the interfacial tension between a liquid and a gas - in the case of quenching, thus collapsing the vapor jacket sooner, and also making the boiling phase faster, starting the liquid phase of the quench sooner.

Why is all this a bad idea for bladesmiths?
Speeding the conversion of phases too fast creates great stresses. In a high carbon steel, the blades will literally tear themselves apart. In a low carbon steel, the softer ferrite can tolerate more of these stresses and will survive. Superquench was mainly designed to harden large parts and objects that have fairly equal distances to the center. This allows more or less equal forces being applied as structures convert in the matrix. Blades are the worst ratio of distance to the center being even.

I am only guessing based on general knowledge and not any charts, but steel at .30% carbon is about where a Superquench has great benefit. By .50% it is getting dangerous to the integrity of the blade. By .60% it will likely crack the blade.
 
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GRapp,
Edge quenching is a bit different than yaki-ire (hamon quenching). The results are similar in looks sometimes, but the clay delays the timing and location of the conversions.
Yaki-ire was developed to create a sword with a very hard edge and soft bendable spine. It also created the curvature. The billet was usually composed of various layers and placements of steels with different carbon content ... with the edge steel having the highest carbon content. The core was often almost pure iron.
In yaki-ire the covered spine stays austenite a bit longer than the edge and converts to pearlite after a delay. The edge converts instantly to martensite, with the phase conversions getting mixed up in the region above the edge. This region of mixed structures creates the hamon and nie and nioi. The timing of the expansion and contraction of the structures creates the curvature -- and sometimes can crack the blade.
When using a mono-steel as we do today, yaki-ire can be a sphincter clenching experience. Broken blades are a part of the learning curve. They never go completely away, and many swords become two smaller blades.

In an edge quench using a shallow plunge of only the edge into a fast liquid quenchant like Goddar's GOOP, the steel is a mono-steel. The edge and slightly above hardens and partially auto-tempers creating a temper line above it. The upper portion converts to pearlite at nearly the same time (having missed the pearlite nose). This process hardens the edge and leaves the upper portions as cementite/ferrite pretty much at the same time the edge becomes martensite. Directly above quenchant, the steel partially hardens and then self-tempers as the heat from above runs down toward the edge. This creates a line that looks like a suguha hamon, but is actually a transition between pearlite and martensite. Timing of how long before you pull the blade from an edge quench determines how much hard edge there is and where the temper line shows (if at all). Cracking a blade is not nearly as likekly with an edge quench, which is why it was the main choice in the days before modern quenchants, HT ovens, and tempering ovens.
The edge quench is very old and the quenchants were always a mix of fats/oils/soaps, and usually lye. Many recipes are just a very fatty soap recipe that has excess lye and lots of tallows and other fats. It had to be heated to make liquid. It also went rancid, which really didn't affect the usefulness, but made a smith really stink at quench time.
Steels then were medium carbon compared to today's higher carbon content. In the old days, alloying was a factor of the ore source, not by design.

Today's blade steels are designed to harden at controlled rates in modern quenchants. GOOP is not really needed, nor is Superquench. Those may come into play when using steel sourced from old farm equipment and other medium and low carbon sources.

The better metallurgical method of getting a nice temper line is to fully quench the blade and then draw the temper with a torch to push a temper line down the blade toward the edge. When the line is almost where you want it, you quickly cool the blade in water. This converts the untempered martensite spine to heavily tempered martensite which is stronger than pearlite. Another method of doing this is to set the edge in a tray with about 1/4" of water and draw the spine with a torch. This assures you won't accidentally destroy the hardness of te edge.
 
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Stacy, you might double check that very last paragraph. I am pretty sure that you can't get a "quench line" or hamon by fully quenching a blade and then torch drawing the spine. The majority of the blade in that situation is tempered martensite, with the edge being untempered martensite A "quench line" as I understand is that transition point between martensite and the pearlite above it. Maybe I misundersatnd something there, like maybe the definition of "quench line". "Temper line", for sure. "Quench line", I don't think so.
 
Related question to this discussion. I’m planning a Wakizashi type blade out of mono-steel .25” 1070 (NJSB’s). If I clay the blade for a hamon and horizontal brine quench, will it arch (bend the spine up)? I’m planning on using a salt brine and it’s a cheap enough piece of steel that I won’t cry if I hear the “tink.”
 
Stuart - Thanks, I typed "quench" where I meant temper. The other places I said temper.

oldschool - A mono-steel blade done as you describe will curve upward.
 
Stacy E. Apelt - Bladesmith said:
oldschool - A mono-steel blade done as you describe will curve upward.
Click to expand...
I need some logic here. Martensite has more volume and pushes out, while the lower volume shrinks in. If the hamon is high, the edge is in danger of cracking. Toothy hamon is then better to allow more movement without cracking. Bend can be controlled by tapering the blade, in height and thickness, to get more bend at handle and less bend towards the tip.
Correct?
 
Joe - sort of correct.
You are correct that the position of the hamon can have an affect on sori and to a small degree breakage. I think it is due to the amount of martensite formed than the shape of the hamon. I agree that the mixed structures in the hamon area are more flexible. Since they start forming before the pearlite conversion in the spine, they might be a bit of a shock absorber. Thus, a wider hamon area (toothy) could provide more cushion.
I'm not sure how much thickness and taper affect breaking blades, but warpage increases as the blade gets thinner. It would affect sori due to the lower total volume of martensite edge. However, a thinner or smaller martensite edge may crack easier under the final stress of the spine conversion.


A VERY simplified explanation is that the different structures have different density.
As the edge cools down past the pearlite nose, it contracts, bending the blade down. The soft austenite spine under the clay yields easily to this stress.
Next the super-cooled austenite edge converts to martensite, which takes up more space than the austenite did, so the edge lengthens...and the blade curves upward dramatically and suddenly.
Then the spine becomes pearlite, and it cools, contracting. It adds a little more curvature. This final stress can literally tear the blade apart. The edge is now fully converted brittle martensite, and the spine is tough pearlite...in the tug of war, the edge loses easily.
The steel needs to be the shallowest hardening alloy possible. As little Mn as possible, and none of the normal other toughening elements, like Cr....and no carbide formers but the iron.

Here is another very short explanation of the formation of sori:
The sori develops as a result of the blade ending with two different steel structures.
Brine or Water is the usual quenchant because of its speed (very fast oil will also work).
When the clay coated blade is brought to critical temperature all the steel is austenite. Upon the quench the blade will bend down-wards. This is because the edge (uncovered by the clay) cools rapidly, contracting as it does (under the clay it is still hot austenite). After a second or two the exposed edge converts to martensite, which is less dense than austenite and rapidly expands (at the speed of sound). This pushes the blade curve upward. The clay covered spine is still austenite. It cools slower and ends up as pearlite. The pearlite contracts because it is denser than austenite and thus makes the blade curve up-wards more. The stress on the brittle martensite edge is extreme. A slight amount of auto-tempering happens because of the IN-2-3-OUT-2-3-IN method of the quench. This helps prevent the edge from cracking ... sometimes.
If all goes well, a straight blade (before quench) will end up with a nice little Sori. The area where the pearlite meets the martensite ends up as troosite (old name for martensite/pearlite mix not used anymore except by old farts like me), which creates the hamon.
If all does not go well there is a sharp PING!!! and half the blade falls into the bottom of the quench trough.

So, a straight blade will end up with a slight Sori. A blade with a down-ward curve forged in will end up straight. And a blade with a little up-ward curve will end up with a tachi size sori. The end result is a product of a bit of luck and a whole lot of skill in forging. At best the smith can still only guess a range of expected sori.



 
I had to break the following info into several posts:

Here is some info I wrote in the past on yaki-ire and attaining a hamon:

Forge - holding the steel in a small forge at an exact temperature for 10 minutes without heating beyond 1425F ,eg., is difficult. Use a full size forge and soak it well for at least 15 minutes. Adding a PID controller to the forge and using a muffle could help.

Quenchant - the quench speed is everything in attaining a hamon. Using any oil will decrease the activity. Using vegetable oil in lieu of a fast commercial quenchant (like Parks #50) will further decrease the results (or virtually eliminate them).
Try to learn the quench using brine. Once you have it just about mastered....you will probably go back to fast oil.

Steel - the steel needs to be as shallow hardening as possible. Little or no alloy content. .70-1.00% carbon, and .30 or less Manganese is the perfect steel, but such a mix is hard to find. The usual suspects are 1070-1095, W-1, and W-2, 26C3.
Alloy steels like 5160,52100, (and, obviously, stainless steels) will not work.

Clay - coat the entire blade with a thin wash coat and let it dry. Recoat the shielded areas with a second coat of clay between 1/16" and 1/8" coat. Too much clay is bad. Too little is rarely a problem.
What the clay is isn't nearly as important as how it is applied.
I like satanite, but APG#36 or Rutland's are also good. Satanite is best, IMHO, because you mix it fresh every time and to the exact consistence you want. Properly applied, it stays on the blade well in HT. Commercial products like Nu-clayer are great but expensive.
Start with a thin wash coat over the whole baled. Mix the satanite to a consistency of cream (very thin). Let that dry (a hair dryer helps). Once dry, add a little more satanite powder to the satanite pot and make it like thin pancake batter or thin sour cream. Apply in a fairly thin layer to make the hamon pattern. 1/16" to 1/8" is all you need. Dry well and HT.

BTW, this procedure is called yaki ire.

Condition of the steel - any blade being quenched needs to be ready for the stress it will be under, but shallow hardening steels need it the most. Properly normalize/stress relieve the blade before the clay coating. Sand the surface smooth and remove every grind mark. Eliminate any possible stress risers, such as sharp corners or edges. Leave plenty of edge meat, about .040", and round the edge. Round off all edges a tad (many folks mistakenly grind the edge and spine to a prefect flat surface, which creates a sharp 90-degree angle with the flat sides). Sharp corners are where cracks will start and snap the blade in half with the dreaded "PING". For the same reason don't put in notches, chouls, or jimping until after hardening.

The quench - Plunge the blade straight in the tank (vertical or horizontal), hold the blade still for about 2 or 3 seconds, to allow the edge to cool below the pearlite nose, and then pull it out for 2-3 seconds. Put it back and let it cool to below the martensite. Don't remove it from the warm oil for at least two or three minutes. Gently clean off any clay still stuck on, and snap temper at 300°F immediately for 30 minutes Do the full tempers for the desired hardness as soon as is practical. Any straightening should be done at the tempering temperature on the second cycle.
Resist the temptation to pull it from the oil/brine and give it a quick grind and dip in the FC to see the results. Cracks will likely form while you do that if the steel isn't snap tempered quickly after quench.

If doing a water quench you will have to work out your own in-out timing. For brine and fast oil I use, IN-1-2-3-OUT-1-2-3-Back in. The immediate post quench temper still applies.
 
MORE INFO:
A hamon forms in shallow hardening steels. Any alloy ingredient will make the steel deeper hardening, and thus wash out or block the formation of the hamon. 5160, 52100, O-1, D-2, and other higher allow steels are not suitable for hamon development.

A short course in hamon formation may be in order:
A simple steel has carbon and iron. Anything else is an alloy ingredient. W2 has about 1% carbon and 98.25% iron. There is also a .25% amount of manganese, silicon, and vanadium (typical assay). These alloy amounts are small enough to have little effect on the hardenability. Be aware that all W2 and other steels don't always have the perfect alloy specs. Get a cert with any steel you buy.

When the steel is heated to about 1450F, the carbon goes into solution, and forms a structure called austenite. Upon cooling the steel can do one of several things. If cooled slower than one second to get below 900F, it will form pearlite, a soft structure of steel. If cooled fast enough to miss this "pearlite Nose", the steel will remain as supercooled austenite until it reaches about 400F, where it will start converting into martensite. Martensite is the hard steel we want for cutting tools. Besides the hardness, martensite and pearlite have different crystalline and visual properties. They also react differently to etching.

Now, when the clay coated blade is heated to the austenitization point, and then quenched in water/brine/fast oil, the edge immediately cools to below the pearlite nose, and at 400F converts into martensite. The clay insulated spine retains its heat, and cools slower, thus converting into pearlite. The junction of the two structures is the hamon. This area is a mixture of fine pearlite, coarse pearlite, and martensite crystals. In my early days studying metallurgy this structure was called Troosite, but now we just call it a mixes structure.
Highlighting the effects of this transition area by proper polishing and etching to bring out the optical characteristics of these structures is the skill required in shiage-togi.
The final hamon you get is somewhat of a mystery, but the methods are not.

I have posted several hamon tutorials in the past, but here is a simple guide for a suguha hamon:

Start with a blade that has been through foundation shaping (shitaji togi to form the basic sugata), and is ready for yaki-ire. Normalize the blade before HT. The condition of the steel before HT will greatly affect the final results. Coarse pearlite with fine grain is the desired structure to start with.

Note - While not everyone agrees, it seems that machine work (grinders and milling machines) can create stresses that show up in the final hamon results. Many smiths make the blade by whatever method they wish (forging is the usual way), and then anneal or normalize the blade. After that they do all the shaping work with stones and files. If you are having issues with blades cracking, try shaping by hand with files and stones.

 
Applying the clay:
Make a simple stand/clamp that will hold the blade by the tang and allow you to work with both hands. The ability to rotate the blade and work both sides is important. A trip to Harbor Freight will yield some inexpensive clamps that rotate. Mount the clamp firmly so you can sit or stand by the blade and do the clay work.
If you are married, or have a good partner, Don't do clay coating in the kitchen.

I recommend that you use satanite for the clay. You will read about AP-green, Atlas/Rutland furnace cement, etc., but satanite is cheap, reliable, and works perfect.

Make a thin mix, about like heavy cream, and apply a wash to the whole blade. Dry with a hair dryer or heat gun.

Thicken the mix with more satanite until it is about like sour cream. Apply this to the spine area, bringing it down toward the edge. Stop about 1/4" before the edge. Do the same to the other side. Use a popsicle stick to smooth the layers to about 1/16" to 1/8" thick. Take your fingers and wipe the edge in a straight line, removing the excess along the edge. This will leave the ha exposed for about 1/4". The pattern you leave in the exposed steel will shape the hamon. Dry the blade with the hair dryer.
Note: If you as doing a blade that you wish to control sori somewhat, you can wipe the satanite off the mune (spine).

Do yaki-ire as desired, keeping the austenitizing temperature on the lower side. For example, 1070 says "1450°-1525°F" Try 1450°F.
After quench, clean the blade and examine the edges for ha-giri - tiny cracks running from the edge inward. If there, discard the blade and start again.

After a snap temper, a light sanding, followed by a quick dip in FC may show the potential hamon line. This is not the final result, just a confirmation of different structures in the blade.

If inspection goes well, do the final shitaji-togi (foundation polishing) - the hamon may not be visible at all at this point. Get all the shaping right at this stage. Removal of excess metal will not be possible in the next stage.

Please Note:
The blade will be getting sharp as you do togi. Use caution as you go, and extreme caution in the final stages of shiage-togi. Misuse of things like hazuya stones and nugui can lead to having no fingerprints ... or fingertips if not done right. Doing a hybrid polish instead of traditional togi on your first several blades is a good idea.

Continue onto shiage-togi (finish polishing), where the hamon will start to re-appear.

Use of a variety of methods and etchants can bring the subtleties of the hamon out in the final steps. Ther are many articles and threads on doing this

General notes:
The hamon will not be exactly where the clay stops. Experience, and your own equipment will teach you how to place the hamon.

If the hamon does not appear to have developed, re-do the clay work and HT.

Note that fast oil is safer, but any hamon will be faint or may not exist at all. Brine will develop the best activity (hataraki). Brine will crack some blades until you get it mastered ... somewhat. Water is wonderful for a hamon, but will break a lot of blades.

More complex hamon, greater hataraki, ashi, and other features can be developed by changing the shape of the edge of the thicker clay line. Make the line wavy and you can get notare; poke it with a stick into small ridges and get Choji or many other patterns; make small lines to the edge with a slightly thinned slurry and create ashi.
Another thing that affects the hamon is the niku (meat) of the blade toward the edge. The amount of thickness and grind shape toward the edge affects the quench and how fast the steel cools. I like a slight apple-seed grind.

Info for polishing the hamon:
I have several articles on hybrid polishing but a short list of the agents that will help develop a hamon are:
Diluted HCl ( 100:1), FC, lemon juice
chromium oxide
red iron oxide
black iron oxide (magnetite)
tin oxide, FC
fine SC grit
3M polishing papers ( 400-8000)
Choji or other pure oil
Flitz polish
1.25" round gun cleaning patches.....lots of them!

Other supplies:
White enamel paint (Testors) and finer sable brushes
popsicle sticks
Tough painters tape to mask areas off (Frog tape)


There are several good books on the subject, and some good DVD's.
A few are:
Walter Sorrells - Hamon (and his entire set on Japanese blades)
Setsuo Takaiwa - The Art of Japanese Sword Polishing (I highly recommend this book)
Clive Sinclaire - Samurai Swords

yaki-ire isn't something you just do and are done. After the claying and quench you need to remove the surface metal and expose the transitions between the martensite and pearlite plus etch to expose the crystals of nie and nioi. The polishing and etching are what exposes the hamon. (I'm probably the last guy alive who still refers to these structures as Troosite)

After quench and removal of the clay you don't have a hamon. You have a quenched blade with surface decarb-oxides-and other features. The transition where the clay line was is often topographical (it is also not likely to be where the actual hamon is). This is just the start and not the finished product. All that surface has to be removed.

After quench and some basic cleanup to 400 grit you may see the hamon sometimes. Often you will see nothing until it is etched. Even if you see it, it isn't usually all that is there.
Use a low alloy low manganese steel. My order of preference for readily available steels is - Hitachi white paper, W-2 (low Mn), 26C3.

Etch with very weak acids. 10:1 FC up to 15:1 is a good hamon etchant for most folks.
100:1 nitric acid is also good.
Other acids used are fresh lemon juice and white vinegar.
The etchant is often worked along the hamon features by rubbing with a pad soaked in the acid. Wear gloves if you don't want stained fingers and mushy skin. Makeup cleaning pads and gun cleaning pads are perfect for shiagi-togi task.

Clay wash with a very thin clay mix and then clay the proposed hamon THIN. 1/16" is more than enough. 1/8" and thicker are far too thick. The hamon does not fall exactly on the clay line and some experimentation will be needed to place it where you want. Steel thickness greatly controls the movement of the hamon (as well as alloying),

Let the clay dry! Use a hair dryer of fan if needed, but let it completely dry before putting in the oven or forge. Fast drying in the forge or flames isn't a good idea. If the clay cracks and falls off too soon in the quench, the spine will cool too fast, and the blade can form no sori ... or even negative sori.

Austenitize on the lower range of the steel using. If the hardening range is 1445° to 1490°, use 1445°. An oven is far better than a forge for this.

Quench in a fast oil. I recommend Parks #50.
Brine is an extreme quenchant and can crack blades. It makes a great hamon, but takes its toll on your nerves and blades. No one like the dreaded TINK.

Interrupt the quench - IN 1--2-3, OUT 1-2-3, Back in until cooled. You may have to experiment with the timing.

Develop the hamon by selective hand polishing with very fine powders. Ther is a whole array of oxides and grit compounds used to get different looks.
I like a frosty duller and darker finish above the hamon (ji) and a shiny polish below (ha). Use the corner of a folded makeup pad to work the area below and above the hamon line to get shiny bright and darker areas. Use a different pad for each compound/oxide. Selective final etching post-polishing can greatly accentuate the light/dark look.
After the first light polishing of the whole blade (somewhere between 400 grit and 1000) leave the actual hamon line alone and work the areas above and below it. This creates a frosted white line for the hamon.
NEVER buff a hamon on a polishing wheel buff. It will wipe out most of the visible details and you will have to start polishing again.

Pro-polishing tips - Use glass or plastic "petri dish" containers for the polishes and oxides. Keep the pad used with that compound in the dish. They stack neatly and store in a plastic small box with all your other hamon polishing supplies. A 20 pack is $10.
Use a pointed popsicle stick on the pad for polishing small and tight areas along the hamon or ashi. I like 22 calibre gun gleaning pads for these areas.
Empty and refill the water dip bowl when you change grits/oxides/compounds.
Use nail polish or model paint to mask the hamon and ashi as needed while polishing above and below it. Remove it with acetone or other solvent when done.
 
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