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jr45acp
08-13-2011, 09:03 AM
Until recently I had access to a proper heat treating and drawing oven. Alas, that is no long available to me. I understand hardening with a torch, e.g. heating and checking with a magnet, etc. The rub is drawing. I see references to heating to a straw color, then allowing the part to cool naturally. The reference to the straw color is sort of open to interpretation. So, the question is, does anyone have a color reference chart they could post or refer me to another source for this?

RussZHC
08-13-2011, 09:15 AM
"Drawing Temperature Color Chart", Google, third item down

www.bvwt.org/PDFs/Hook%20Tool.pdf

Edit: that was for wood working tools, if that makes a difference to you. Its not nearly as complete as the listing is say "Machinery's Handbook" , which, at least in my version, also shows temps of Lead Bath Alloys and "Tempering Temperatures for Various Tools" (in the general "Heat Treatment of Steel section, in mine is P 1454 or so)
Pale straw is 450*, Straw is 460*, Deep straw is 470* to use your example

Dr Stan
08-13-2011, 10:39 AM
You could get some temp sticks. They look like over sized crayons and are made to melt at specific temps. An IF thermometer may also be useful.

jr45acp
08-13-2011, 10:56 AM
Thanks for the feedback Gentlemen. Actually, my current project is making a cutting tool for scrimshaw. I suppose, as with many things, I'll play around with it and go from there. It probably doesn't help that I'm working with mystery metal from my scrap, but I'm 90% certain that it was tool steel. Before I annealed it to begin shaping the cutter it was harder than woodpecker lips. My best file just skidded across it. Temp sticks are probably the best approach in the long run, but with the economy, etc., I was trying to save money.

gwilson
08-13-2011, 11:10 AM
I used Tempilac brush on lacquer many years ago. Trouble was,when the stuff melted,showing the correct temperature,it would etch an ugly scar into the metal. I hope the crayons don't do that like the liquid,paint on stuff did.

Depending upon your metal type,different steels can look different colors at the same temperature. In reality,there is only a 25 degree "gate" to get optimal results from a given steel. Unless you are making a super expensive set of dies or punches,though,you should be o.k..

JCHannum
08-13-2011, 11:32 AM
Here is a chart giving colors for "carbon steel", but as George mentions, different steels produce different colors.

http://www.anvilfire.com/FAQ-article.php?bodyName=/FAQs/temper_colors_hardness.htm&titleName=Temper%20Colors%20and%20Steel%20Hardness %20:%20anvilfire.com

For smaller parts, a toaster oven and a good thermometer can give reasonable results. For your purposes, temperatures in the 400-600*F ranges can be achieved with this combo.

gwilson
08-13-2011, 11:49 AM
I use a toaster oven with an inserted high temp. thermometer from Brownell's Gunsmithing Supplies. It has a long thermocouple rod on the back side.

You cannot trust the thermometer on ANY kitchen type oven. They can be 75 degrees off.

codarnall
12-02-2011, 10:10 PM
I am having great success with my new Paragon SC2 kiln. At issue is finally stainless steel 309 envelopes have solved carbon and mill scale issues.
The question I have is does anyone know how many times the SS packets can be used?
I tried what I thought were SS cans but I think they were just nickel plated.
I am heating at 1750F for 20 minutes for A2.
Regards,
Charlie

tdmidget
12-02-2011, 10:18 PM
20 minutes? How thick is the piece?

Evan
12-02-2011, 10:23 PM
Here is another chart with larger colour patches. Makes it easier to compare. Comparison should be done inside under normal lighting. Outside it's too bright and the colour is altered by skylight.

http://ixian.ca/pics7/colortemp.jpg

Mcgyver
12-02-2011, 11:00 PM
I'll go out on a limb here and most of the those published colour charts for tempering are hogwash - toss 'em. My own experiments, and a brief little blurb in the ASM volume on heat treating say the metal does not go through infinite colour changes but that its a step change. Here's a polished 10" long bar i heated from one end, there are only a few colours and they're distinct.

As industry doesn't rely on colour for temp, this is done in a timed temperature controlled ovens, its not something you'll find much current authoritative info/research on, but try it yourself if you doubt.

Also, tempering is NOT just temperature dependent...its time as well. Left long enough at a straw colour temp, it'll eventually let down to the same rockwell as another high colour temp used for a shorter time

For the OP, its less confusing that an endless spectrum suggests

here are the ASM colours presented as a step change

Approximate Colour F C
Faint straw 400 205
Straw 440 225
Deep straw 475 245
Bronze 520 270
Peacock 540 280
Full blue 590 310
Light blue 640 340
Grey 700 370

my experiments

http://i785.photobucket.com/albums/yy132/michael01000/DSC_1807-large.jpg

http://i785.photobucket.com/albums/yy132/michael01000/DSC_1809Large.jpg

tdmidget
12-02-2011, 11:09 PM
+1 for McGyver. Early 1903 Springfield rifles are known for actions exploding for this very reason. They were heat treated by "eye" and they were not consistent. People see colors differently and lighting as Evan said can change every thing. In an era when an IF thermometer can be had for peanuts it makes no sense to gamble.

38_Cal
12-03-2011, 12:45 AM
For small stuff, including gun springs, I use a Nitre Blue bath, chemicals from Brownells. Molten at around 275 F., useable up to about 800 F. Low temp stuff would take a heavy steel or stainless steel saucepan on a hotplate with a good lead pot thermometer to help control temperature. The stuff is actually a heat treat salt compound.

David

Tait
12-03-2011, 01:13 AM
Is the steel likely a carbon steel, or is it a highly alloyed steel?

I'm pretty sure the heat to magnetic, then quench plan is OK with 1080, but doesn't work as well with O1, and is way off with D2 and other chromium alloys.

Evan
12-03-2011, 01:37 AM
Tempering by colours is very approximate since the colour change is highly influenced by the alloy ingredients. Even though carbon steels are not considered alloy steels they still have small percentages of other metals intentionally added to obtain certain properties. Foremost is manganese which may be as high as 1.6% without the steel being considered alloy steel.

These ingredients will change the alloy colours for a given temperature. I don't agree on the step change idea as my experience is that it can be very continuous. Again, that may depend on the alloying ingredients but this example is pretty smooth on the colour change.

http://ixian.ca/pics9/harley2.jpg

Which colours show up will vary with the heating rate and what contamination might be present on the surface too.

small.planes
12-03-2011, 08:01 AM
For just drawing the temper (pale yelow / light straw) ensure SWMBO is out, then go and put the chip pan on, most go to around 200 - 250 C (400-450 f)

Then fry until cooked ;)

Dave

Highpower
12-03-2011, 11:24 AM
For small stuff, including gun springs, I use a Nitre Blue bath, chemicals from Brownells. Molten at around 275 F., useable up to about 800 F.
Are these salts re-useable, or a one-time deal?

oldtiffie
12-03-2011, 05:52 PM
I think that some Blacksmiths etc. are not going to be too pleased at all to find out that they can't "forge" harden and "temper" ("draw") a bit of steel either.

Not just Blacksmiths either.

I agree that a good adequately-sized thermostatically-controlled "oven" is the ideal but care with an oxy-acet torch and a bucket of oil or water can do very well.

If the hardened and/or tempered/drawn job done with a torch is adequate for its intended purpose then by pretty well any measure it is a successful outcome.

Not everyone want or needs - or can afford to buy and operate - an "oven".

J Tiers
12-03-2011, 09:46 PM
If you are trying to temper small stuff...... particularly thin small stuff that is of considerably larger dimensions L & W than thickness..... like a small leaf or bent type spring, or the like.

What you want to do is to get a plate of metal of reasonable thickness for it's size, which the part(s) will fit nicely on with extra room.

now polish the topside with sandpaper so you have clean metal.

Lay part on it, and start heating bottom side with torch.... watch colors ON THE PLATE, and stop just short of what you want.... there will be a little more heating as the heat gets thru the plate. The part will then change color pretty much along with the plate, fairly evenly, and you can dump it off when done.
.
.
.


I disagree about "step" changes...... the changes are gradual, but there is a range of each, but NOT an equal range between.... not a "step", but also not a "continuous and even variation" between colors......

JCHannum
12-04-2011, 09:40 AM
Are these salts re-useable, or a one-time deal?

The salts are reuseable. They are used for bluing or black oxide. They are rather nasty unless you have an area dedicated to their use.

In the same vein, if you have a lead pot available, molten lead can be used to heat soak for tempering.

I use an iron pot filled with fine brass turnings for small parts. Put the parts in the turnings and heat on the kitchen range using a good quality temperature probe. Heat to desired temp and allow to cool. Parts can be laid on top if you want to observe color changes rather than go by temp, quench when desired color is reached.

Highpower
12-04-2011, 10:53 AM
I have a couple of lead furnaces and tons of lead, but that is only going to be useful above 621 F. I was think more in terms of the lower temps for the small springs and such. The brass shavings sound like a great idea though, as does the bar stock heating plate.

lazlo
12-04-2011, 11:33 AM
Also, tempering is NOT just temperature dependent...its time as well. Left long enough at a straw colour temp, it'll eventually let down to the same rockwell as another high colour temp used for a shorter time

That's most definitely not true Mike. You can't over-temper.

I've accidentally left blades in the temper oven for several hours, and they're the same color and hardness (on my Wilson) as from 1 hour in temper.

lazlo
12-04-2011, 11:38 AM
Is the steel likely a carbon steel, or is it a highly alloyed steel?

I'm pretty sure the heat to magnetic, then quench plan is OK with 1080, but doesn't work as well with O1, and is way off with D2 and other chromium alloys.

That's true -- the higher the alloy content, the farther the austentizing temperature is from the curie point. Austintenizing temp is when all the carbon is in solution, Curie is where the metal goes non-magnetic.

Higher alloys like O-1 ("drill rod") also need a 20 minute soak (depending on thickness) to get everything into solution, and you can't do a soak with a torch.

That said, you'll get plenty of hardness out of O-1 heating it to non-magnetic and quenching in motor oil.

Evan
12-04-2011, 11:42 AM
With alloy steels the amount of chromium strongly affects the colours produced. The more chromium the more it raises the temperature for a given colour. Really, you can't use colour as a guide to tempering alloy steels.

Mcgyver
12-04-2011, 11:42 AM
That's most definitely not true Mike. You can't over-temper.

I've accidentally left blades in the temper oven for several hours, and they're the same color and hardness (on my Wilson) as from 1 hour in temper.

it most definitly is true ...its right out of the ASM volume on heat treating - the times are longer than what you've used, but the degree of reduction in hardness is both temp and time dependend....you will achieve same hardness low temp +long time as higher temp short time. Its a curve - you're not going to a 10 rockwell swing in an hour, but it is how it works.

lazlo
12-04-2011, 11:48 AM
it most definitly is true ...its right out of the ASM volume on heat treating

I've got the ASM Heat Treater's Guide in my lap Mike -- you're reading the chart wrong.

The TTT diagram at the top for austentizing is time/temperature critical.

The tempering graph at the bottom is not time dependent -- it's strictly temperature dependent.

http://www.wisetool.com/ebook_stamping/art54-p5.gif

Mcgyver
12-04-2011, 12:07 PM
I've got the ASM Heat Treater's Guide in my lap Mike -- you're reading the chart wrong.

The TTT diagram at the top for austentizing is time/temperature critical.

The tempering graph at the bottom is not time dependent -- it's strictly temperature dependent.




keep reading.....




http://i785.photobucket.com/albums/yy132/michael01000/asm1.jpg

http://i785.photobucket.com/albums/yy132/michael01000/asm2.jpg

lazlo
12-04-2011, 12:15 PM
http://i164.photobucket.com/albums/u15/rtgeorge_album/asm2.jpg

So look at at 1 hour at 315 C -- you get 56 Rockwell. Leave it in for another hour and you get 55.5 Rockwell. Leave it in for 5 hours and you get 55 Rockwell.

That's why the ASM Heat Treater's Guide doesn't bother listing time on the temper graph.

Mcgyver
12-04-2011, 12:37 PM
As I suggested you didn't see a difference in your example because of where on the curve you were - however you started off contradicting what i said as "most definitely" being incorrect, that's far worse that just plain old definitely being incorrect. :D It wasn't and isn't. Picking a flat part of the curve doesn't alter how it works or that its very material at other places on the curve. Being aware its temp and time dependent is the important part as there a lots of non linear parts to the curve. I don't have a furnace so rely on crudest of approaches - still its valuable to know that such and such desired Rockwell is very different at 10 second vs 1min vs 1 hour. I suppose in a commercial setting a trade off enters of cost vs accuracy as well

lazlo
12-04-2011, 01:02 PM
As I suggested you didn't see a difference in your example because of where on the curve you were - however you started off contradicting what i said as "most definitely" being incorrect

It most definitely is incorrect. Temper is, for all practical purposes, time independent, which is why the ASM Heat Treater's Guide doesn't list time on the temper graph (I posted above).

I have a bunch of pictures of knives I've tempered at the same temperature for 1 hour, 2 hours, 4 hours, and multiple times at each temper (just depending on what was going on in the forge at the time). All came out the same golden color, same Rockwell. I'll upload later today.

Tempering is also not discrete, as the other posters have pointed out.

lazlo
12-04-2011, 01:22 PM
Sorry for the dirty fingernails, I'm in the shop...

http://i164.photobucket.com/albums/u15/rtgeorge_album/ASM1.jpg

http://i164.photobucket.com/albums/u15/rtgeorge_album/ASM2-1.jpg

http://i164.photobucket.com/albums/u15/rtgeorge_album/ASM3.jpg

http://i164.photobucket.com/albums/u15/rtgeorge_album/ASM4.jpg

J Tiers
12-04-2011, 02:19 PM
Chill it.......... (pun OK)

You are arguing over an asymptotic curve.......


Like an R-C charging circuit...... it "never" gets actually to the input voltage......in finite time.... (ignoring the quantized value of "charge")........ but it gets close enough for the most precise applications fairly quickly.

Most likely the curves don't show time because the assumption is that you will leave the part at temp "long enough to be stable".

The real question is whether the temp for 55 Rockwell will reduce it more after 6 months, or 3 years.... and if so, by how much.

codarnall
12-04-2011, 03:03 PM
20 minutes? How thick is the piece?

The pieces are A2 oversize, walls are at some points 1/4 inch thick and other points are as thin a .050. Form factor /picture are on freechex.net.

Charlie

Evan
12-04-2011, 03:05 PM
Temper is, for all practical purposes, time independent, which is why the ASM Heat Treater's Guide doesn't list time on the temper graph (I posted above).

For once I agree with Robert. If those nice straight downward sloping curves were plotted on a linear scale they would be visually flat (level) even if the chart were ten feet wide. That is why they had to use a log scale to make the difference show up at all. Technically it is time dependent after an hour or so. In the real world it isn't unless you leave it in the oven and go on vacation.

lazlo
12-04-2011, 03:20 PM
For once I agree with Robert.

Looking outside to see if Hell has frozen over... ;)

Mcgyver
12-04-2011, 03:41 PM
If those nice straight downward sloping curves were plotted on a linear scale they would be visually flat (level) even if the chart were ten feet wide. That is why they had to use a log scale to make the difference show up at all.

thats garbage. 10 seconds vs 60 equates 5 on the rockwell scale - kind of obvious that isn't flat. Anyway, my assertion was and is correct that its temp and time dependent. That a chart shows hardness varying with temperature is hardly evidence time isn't also a factor. They both are as the ASM volume clearly says.

Whether at the length of time you're considering makes it relevant or not to you application is irrelevant to the original assertion. This fact, that it is time & temp sensitive is very much a pragmatic real world thing to be aware of as people are suggesting letting it reach temp then quench - which will produce quite a different temper than if held for say 60 seconds. look it up on the chart i provided

you should agree with Robert a lot more, he's credible and usually right. On this one he didn't have full info, made an aggressive challenge and on being caught is deflecting it to whether its relative or not to a particular situation. Frankly that doesn't confront me; its relevance to any particular situation was not the assertion I made and was contradicted on.


I don't agree on the step change idea .
.

of course you don't. but present something other than a contradiction. I think your erroneous belief is held in part because we normally see the group of colours as a narrow band, and it looks like spectrum....but if you try to elongate that band like I did in the photo's it clearly shows the colour jump from one to another in definitive steps, there is no transition.

Even where its on the edge you see peacock and blue spots interspersed, not some shade in between! Unlike many here, I'm always prepared to wrong, just doesn't matter that much to me - what i presented is my own experiment plus readings from the ASM books. So show me evidence or authoritative info to the contrary. Until i see it, I think those nice spectrum's in the books are just that, there because they look nice (for temper temps, not hardening) and don by an artist instead of metal worker

J Tiers
12-04-2011, 04:52 PM
of course you do. but present something other than a contradiction. I think your erroneous belief is held in part because we normally see the group of colours as a narrow band, and it looks like spectrum....but if you try to elongate that band like I did in the photo's it clearly shows the colour jump from one to another in definitive steps, there is no transition.

Even where its on the edge you see peacock and blue spots interspersed, not some shade in between!

The colors are different "compounds" or forms thereof...... so, yes, they can be only one or the other...... but it doesn't matter.......

The relative amounts give the shades..... It is NOT NOT a case where everything is straw until 336.50076543 degrees (or whatever) and then at 336.50076544 degrees it all changes to the next color.... with a sharp line. You may be able to get that if you try to, but in normal tempering, I have never really seen it.

As with most such things, it is no doubt a matter of relative probability, so temperature and local conditions on the material affect how much changes to the next color at any given time. hence the "gradations" that most (not you, apparently, being an all black/all white/no gray kinda guy I guess) see.

The gradations are a matter of how much has changed. Since they are often visible as these "gradations" a on a piece heated from one end, they effectively give temperatures, if you care to observe them.

JCHannum
12-04-2011, 05:45 PM
Technically it is time dependent after an hour or so. In the real world it isn't unless you leave it in the oven and go on vacation.

It is a factor in applications where the material is exposed to temperature cycles which approach the drawing temperature, in which case, the accumulated time at temperature can result in eventual decay of original properties.

Evan
12-04-2011, 08:20 PM
of course you don't. but present something other than a contradiction. I think your erroneous belief is held in part because we normally see the group of colours as a narrow band, and it looks like spectrum....but if you try to elongate that band like I did in the photo's it clearly shows the colour jump from one to another in definitive steps, there is no transition.

Even where its on the edge you see peacock and blue spots interspersed, not some shade in between! Unlike many here, I'm always prepared to wrong, just doesn't matter that much to me - what i presented is my own experiment plus readings from the ASM books. So show me evidence or authoritative info to the contrary. Until i see it, I think those nice spectrum's in the books are just that, there because they look nice (for temper temps, not hardening) and don by an artist instead of metal worker


You are mistaken. The spots you see on your sample are caused by variations in temperature. Slight differences in surface finish affect radiation as well as differences caused by grain orientation. Rolled steel isn't perfectly isotropic and the sample you show isn't very smooth either.

Just polishing the sample makes a big difference. Also, one must be very careful when interpreting images created by a digital camera. The image is inherently quantized and there are only 256 steps for each of the primary colours. More importantly, the average digital camera is set to enhance contrast and saturation. That has the effect of reducing the dynamic range even more so that there are fewer steps to represent colours.

This is a piece of ordinary low grade steel that I polished and heated over my gas kitchen stove. It has a very continuous range of hues and that can be verified by the histogram of the image. The hard cutoff at the left of each colour curve is a function of the noise reduction processing in the camera to prevent "hot" pixels in the dark areas of the image. Otherwise, all colours to the right of the cutoff are well represented meaning there is a full range of colours present.

http://ixian.ca/pics9/heatcolour.jpg

Mcgyver
12-04-2011, 10:29 PM
the piece you present has the same colours as mine, an no others; no shades in between those the ASM says you'll see. Pixel mumbo jumbo doesn't cut it, my original appears the same as in my picture...very distinct colours without shades in between. Your polished piece presents the same information,

JT, all I want to do is see things as they are


The relative amounts give the shades.....

of course, but the shade of any point is temp dependent and the changes take place in steps. That's all I said. You can see peacock and blue interspersed suggesting it either peacock or blue, a step change. Many of the commonly found diagrams would lead one to think its continuous spectrum of colours.


It is NOT NOT a case where everything is straw until 336.50076543 degrees (or whatever) and then at 336.50076544 degrees it all changes to the next color

you know this how?

I gave the ASM temps at which colour changes take place. The weren't to absurd decimal places. The info I presented suggests you will see peacock from around 540 to 590, at around 590 you start to see blue. You don't see some shade half way between peacock and blue at 565 is the point, you see peacock. Which you agreed with in saying
The colors are different "compounds" or forms thereof...... so, yes, they can be only one or the other......

Finally, I didn't mention this fact to go through the 20 pages of dribble and drivel that can happen here, only to encourage the newbie that its not that hard, and don't crazy looking for some specific shade some erroneous spectrum suggests is out there, there only a couple that you'll see.

anyway, nothing more i can add on this topic, over and out

J Tiers
12-04-2011, 11:21 PM
Many of the commonly found diagrams would lead one to think its continuous spectrum of colours.

There are enough to make the difference between what happens and a "continuous spectrum" of interest only to a person who wants to split half-hairs into microns.......



you know this how?


By observation..... there does not seem to be a sharp line, there is a "transition region".... Possibly that is due to microscopic interspersed areas changing. Possibly THAT is in turn caused by intermediate temperatures..... that is certainly what it looks like.

By reasonable good sense..... it is a chemical reaction, so it is some form of equilibrium..... and typically will have some range of conditions over which the equilibrium "tilts" from one to the other..... Can of course be small, but apparently is not, since there is a visible transition region in most cases.



I gave the ASM temps at which colour changes take place. The weren't to absurd decimal places. The info I presented suggests you will see peacock from around 540 to 590, at around 590 you start to see blue. You don't see some shade half way between peacock and blue at 565 is the point, you see peacock.

The entire process is not one calculated to give a "slidebar" choice of colors..... that you can get any shade of...... The 8 different varieties you yourself posted is sufficient proof that there is a goodly range of color, never mind the "half and half" intermediates.




Finally, I didn't mention this fact to go through the 20 pages of dribble and drivel that can happen here, only to encourage the newbie that its not that hard, and don't crazy looking for some specific shade some erroneous spectrum suggests is out there,there only a couple that you'll see.

There are several, and some gradations of each..... Yellow-brown, purple, blue.......... with gradations of "light straw", "dark straw", etc..... your OWN picture and the H-D plaque picture both show that....

The ASM list you yourself posted shows 8 different colors or gradations...... Should be enough for anyone, and DEFINITELY not "only a couple that you'll see", as you state in the quote.

Perhaps, if there are only a "couple" that will be seen, you would like to point out which two of the eight choices in YOUR posted ASM list are the only "couple" you will (ever) see?

Evan
12-05-2011, 12:05 AM
Pixel mumbo jumbo doesn't cut it, my original appears the same as in my picture.

"Pixel mumbo jumbo" is the only way to tell what colours are in there. That is why they use paint colour comparators to mix paint. By the time the image reaches your or my screen there isn't nearly the same colour gamut available to represent the colours. The printed colour charts have the same problem. It is entirely impossible to print a colour chart that looks the same as a hot piece of metal.

Sure your original may appear to have steps but it doesn't look that way because of some sort of stepwise colour change with temperature. To start with there isn't a plausible explanation why it should be so as an inherent property of the metal.

The colours are a result of progressively thicker oxide layers that act as an interference filter that traps most colors while reflecting on one small range of wavelengths. To produce a stepwise change in the layer thickness would require the formation of crystalline ordered arrays of Fe3O4 oxide molecules that would be far larger than the crystals on which they rest. The crystalline arrays would also have to remain ordered in 3 dimensions, one atop the other through thousands of layers to produce a range of colours. Then the layers thousands of molecules thick would have to avoid forming some thicknesses and prefer others. That simply doesn't happen.

In reality the oxide layers are amorphous and form through a continuous range of thickness. That means all colours are both possible and present.

The chances are good that there are colours present that you can't see, the same as most people. Having passed a standard eye colour test means nothing except that you can discern gross differences. The apparent match between the physical part and the image on the screen is entirely due to the adaptability of your eyes and brain. In objective reality, they don't even come close to matching.

The digital analysis shows without a doubt that all the shades are present in the image and that isn't nearly as smooth as the actual part. If it really was stepwise then the colour curves would have notches dropping to the bottom of the graph.

Your impression that not all the colours are present is also due in part to a lack of full saturation.

This diagram below shows the colour gamut for various methods of displaying colour compared to what we can see with our eyes. Of course, the colours in the diagram are not accurate because it is impossible to show them on your screen accurately. It gives only a relative indication of how well colours may be represented. Also, the outside circle which contains the colours that a human can see is an average and does not represent what any one person can see. Any one person will have bumps and hollows around the outside curve that represents how they perceive colour. The RGB gamut is what your monitor can produce, at best. The Pantone gamut is what the best industry standard printing inks can produce and the CMYK gamut is the best your printer can do.

http://ixian.ca/pics9/gamut.jpg

At any rate, arguments about subjective colour start and end at the same point, the observers brain. No two people see colour exactly the same and no one person sees it the same all the time. Even one's eyes differ in colour perception. That is why colour tests are done one eye at a time. In particular, men have a large variability in the perception of red and green.

Mcgyver
12-05-2011, 12:11 PM
Perhaps, if there are only a "couple" that will be seen, you would like to point out which two of the eight choices in YOUR posted ASM list are the only "couple" you will (ever) see?

Couple was the wrong word, a hand full or finite number would be more exact. Minor semantics though, given i presented both images and list of how many i expect to see. I think they may well vary slightly by alloy, but you'll find a finite number for a given alloy. I found the results interesting when you try to get the progression of the zone of colours over a wide area, combined with the ASM's info contrasted against the rainbow view that appears on the back of say "Hardening and Tempering Engineers Tools" and other publications....again the intent was to simplify not obfuscate so some newbie trying his hand at it wasn't looking for things that don't seem to exist