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Linseed Oil Application (basic)


LA9436

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A quick question,

Are there any basic tips or tricks to applying linseed oil to hot metal?
I am trying to apply the oil to a piece of 40mm x 3mm x 500mm bar stock (1.5'' x 1.1'' x 19.6'') but I can't get an even coverage. Some parts of the bar stock will be very black, and other parts look like they barely have any oil on them. Here are the steps I take;

1. I heat the metal as evenly as I can.
2. I move the metal onto my anvil
3. I soak some linseed oil into a rag and then gauge the heat of the metal by seeing if the oil evaporates when applied.
4. As soon as the metal is cool enough to not evaporate the oil, I quickly wipe the metal with lots of oil.

Am I doing something wrong? And a side question, would it be more practical to use a spray bottle instead of a rag?

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It important to keep the piece as uniformly hot as possible, so setting it on the anvil or uneven application of cool oil causes problems with color uniformity.  If the piece is too big to dunk in oil, I prefer to spray the oil.  I get a much more even looking result that way.  I use a "Sure Shot" sprayer.  Its refillable and holds about a quart of oil.  Various spray tips are available. 

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Ditto not laying it on the anvil to oil! Hold it with tongs at least though a wire cooling rack works well. Depends on the piece as to "best: application method. Dipping works very well if you have the container to submerge it all at once. I use a paint brush on some projects but spray works for most everything. 

A word of caution about spraying an oil mist in a room with a forge burning. It can be an extreme fire hazard! You need to give thought to where the mist will go and how to control it. 

Frosty The Lucky

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Thank you for the replies.

Thank you gm for making my aware of the sure shot. This looks very convenient and I will likely purchase one regardless.

Dipping sounds like it is the preferred method. Does this method have to be timed right, or can the metal be dipped even if the oil will evaporate upon contact?

What bristle material would you recommend Frosty? I would also like to try this method.

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Non synthetic brush! Bristle seems to the be the common term for organic though I recommend against HAIR BRISTLE!:wacko: (we really need a few more emojies like a bad smell one that isn't a pile of poop) 

You don't need to worry about oil smoke or a flash over burst of flame if you submerge it completely quickly. When I was doing a lot of coat hooks at demos I made a wire bottom with handles that stick up above the oil level in a gallon paint can. That way I could jut drop the hooks in the oil, leave them until I had a moment or delivered to a "commissioner" and I pulled the wire "basket" out by the handles. 

Normally I don't finish with BLO but there are times it's requested so I went prepared. I checked for temp with a wood splinter about wood match size, I lay it against the part and depending on how quickly it browned or charred indicated the temp well enough to get the color finish I was looking for. Don't ask me how fast, it's been years and I'd be guessing. Experimenting is easy.

My preferred finish is the "bees wax, Neatsfoot oil, turpentine and lamp black (soot)" recipe found in Bealer's "Art of Blacksmithing." He calls for BLO but said almost any polymerizing oil works fine. I didn't have beeswax for the first batch and used paraffin instead and it's held up outside nicely since the mid 90s. My latest batch doesn't contain soot, it was a major PITA to make and collect and without looked well. Oddly enough a few years ago I was shopping at an art supply for colored modeling clay and discovered two shelves of graphite powder and in different colors. If you actually want to add Mr. Bealer's "Lamp Black," the graphite is the same basic thing and so MUCH easier to acquire.

Frosty The Lucky

 

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Frosty,  to pick a nit, carbon black ("lamp black") and graphite are not the same thing although they may both work fine as a colorant for a steel finish.  Graphite is a naturally occurring crystalline substance which forms small "platy" bits which is why it is used as a lubricant.  Carbon black is basically soot formed by the incomplete burning of oil, natural gas, or coal.  It is most commonly used as a colorant in things like tires and is available via the internet.

There is a small town in NE Wyoming named "Alladin" which was founded by the Alladin brand of stove black in the late 19th century.  They were burning natural gas to produce soot for the product to blacken coal stoves.

"By hammer and hand all arts do stand."

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Where I grew up in W TX, back in the 40's, maybe as late as the 50's, there was a huge carbon black plant near a highway.  As I understand it, the plant used natural gas from the surrounding oil and gas fields.  I can recall the humongous black clouds of smoke coming from the ovens, completely obliterating the sunlight at times, looking like night time.  When the black smoke clouds blew across the highway, it was a real safety issue since you couldn't see the cars ahead of you.  Everyone had to turn their headlights on.  Talk about pollution!!!!!  All the plant life, mesquite trees/bushes, greasewood bushes, grasses, etc. around the carbon black plant had a thick coating of carbon black...looked surreal, like something out of a sci-fi movie.  I don't know if any of it was still living or not; probably not, just preserved.  We always held our breath as long as possible, with the windows rolled up, when driving through the cloud.  The plant has long since been gone, thank goodness.

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I wonder if black toner powder would work.  It is VERY fine and VERY black.  I wouldn't be surprised.  However, I am not sure of what it is chemically and if it might react with linseed oil.  If you had a borked toner cartridge that still had some toner powder in it it might be worth an experiment.

GNM

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Your problem not getting an even heat is a common problem solved by experience.  

I use a rag, and start applying the finish when the black heat is too hot. It smokes off and remains grey. When it is the correct temp, it isn't glossy (too cool), nor grey (too hot). Go as far down your bar as you can until its too cool. Then take another heat beyond your finish and let the heat travel back to the finished part. Keep applying your finish as above while the heat travels twards you until you run out of heat. Then repeat until you are done. This is the best way I know to learn how to apply your finish. 

Also, I use a 50/50 blo / turps with beeswax melted into the mix. I put a quart of both into an old paint can with the lid handy with about a walnut to an egg size of beeswax on the top of my coal fire. heat gently until the beeswax melts. If it flashes, I remove the can with my poker via the paint can bale and put on the lid. The proportions really don't matter. I prefer a liquid. It flows better under collars and into the mortise if you are using tenons. On handled iron such as fire tools and door/cabinet hardware, the beeswax picks up your body temp and creates the effect that the iron is warm, not cold. 

When cool, I usually clean it with denatured alcohol to remove the grime and apply a coat of a carnuba based furniture or auto polish. If you rub it a bit when do these final steps it will bring out the highlights in the steel for an added touch.

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  • 3 months later...
On 9/16/2022 at 3:23 PM, George N. M. said:

to pick a nit, carbon black ("lamp black") and graphite are not the same thing although they may both work fine as a colorant for a steel finish.  Graphite is a naturally occurring crystalline substance which forms small "platy" bits which is why it is used as a lubricant.  Carbon black is basically soot formed by the incomplete burning of oil, natural gas, or coal.  It is most commonly used as a colorant in things like tires and is available via the internet.

My day job is a HVAC technician and have been on many service calls where furnaces or fireplaces weren’t burning right and everything sooted up. I’ve cleaned a lot of soot in in my trade but never thought about keeping it. (If I only knew?)

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Anvil  Use a rag, and start applying the finish when the black heat is too hot. It smokes off and remains grey. 

Red heat, visible in the dark is 752*F on the Halcomb scale.  Black heat on that scale would be below 752*F. 

I have heard that it is black heat up to 1000*F as a talking point

 

Turpentine will be flammable as soon as it reaches the flashpoint that is 86*F to 115*F (30-46 degrees celsius). If it reaches the temperature and starts the ignition,  it will last until all the fuel burns out.

Beeswax softens at 90 deg F (32 C) and melts at 143 to 151 degrees Fahrenheit. However, if you let it heat till its flash point— a higher temperature of about 400 degrees Fahrenheit, you could be calling for an explosion as the beeswax will ignite into flames. 

Linseed oil ignites at 200° F. That means if the temperature goes close to 200°F.  The typical flashpoint of linseed oil is approximately 200 °F (93.3 °C). Flashpoint means the temperature at which a liquid ignites without warning when in contact with air.

Black heat on that scale would be below 752*F.  If it flashes, I remove the can with my poker via the paint can bale and put on the lid. 

 

All three ingredients have a flash point about 500*F lower than the temperature you are using.

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Glen, not sure if I understand your details. A small correction. A black heat is a wide range of temps from, accepting your numbers, to basically dead cold. how do you know when a black heat is at the correct temp? That question is answered in my first sentence, when your experience level is high enough. 

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There is a difference between just starting to smoke, just a little smoke, and rolling smoke. 

Applying wax or oils at the melting points allows it to flow into and the small areas. It is an easy way to provide better coverage to the metal and therefore protection.   One question that keep coming up is when wax or oil and it smokes, what is left on the metal after the wax or oil vaporizes to smoke?  

Experience level is sometimes difficult to put into words and pass that experience on to others.  Visual aids are one way.  Too hot to hold is subjective depending on the individual.  When using a wood cooking stove, the cooks can "feel" the right temperature.  Those using an open fire to cook on or with or wood fired pizza ovens learn by feel when the temperature is right or if the time needs adjusted without consulting a clock.

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There's the problem with your above description of "black heat," Glenn. Suitable temperature and results are too subjective to quantify with numbers like you did. The ONLY way to make this work unless you're using automatic machinery is by trial and error. Anvil's method describes exactly that on a per piece basis.

An old acquaintance used to heat his work in a kitchen oven in baskets and dunk them in oil by the basket load. He learned the technique when he learned the trade so he had it down to "exact" temperature and dunk time to get the results he wanted. 

I deal with variations in in product temp by first touching it with a corner of my application rag if it smokes heavily I dunk it completely quickly to prevent ash it drips off when I remove it and I wipe the excess and "polish" it with the other rag. If I just get that whiff of turpentine vapor I wipe it on with the application rag. It's all subjective and case by case. 

People starting out in any craft want by the numbers instructions and it's too often a disservice to try to give provide such. Short cutting the learning curve rarely shortens or flattens it.

Frosty The Lucky.

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Let is go back to the basics, and use mild steel.  Let's call black heat, as heat from ambient temperature to temperature that does not show color.  You need to throw in normal room lighting, or lighting in shadow conditions, into the mix. 

The only way to insure repeatability as to touching it with a corner of my application rag and watch for the smokes heavily amount of smoke.  Once that happens, then to measure that heat, which should give you a number in degrees. Hit that number the next time and you are good to go.  

This is true with many crafts, tighten the bolt to snug or use a torque wrench, set the temperature of the oven to bake a cake, or use an oven thermometer to be sure, driving down the road at a speed or looking at the speedometer, etc.  It is not shortening a learning curve but starting out at a known standard, or a reference point.

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So I think I understand your point here and I agree with all you have said.  That is when you are starting out cold, so to speak, you are suggesting the use of a thermometer to find that nebulous correct temp to apply your oil. That is a way to do it. And it will work.  However it just might not be the best way. Thats my opinion. Especially when solving the problem of a consistent finish on a long piece of iron, which is the original question. By long, I mean any piece of iron that takes multiple heats to apply your finish. And it is a problem to get a consistent color finish on a long piece of iron. This problem is solved by understanding temp and,, most important,, by the technique you use to apply your finish and  heat your iron.

Heres my technique for getting a constant finish on a long piece of iron, lets say a 10' cap rail 1/2"x2" with champfered edges. It works just as good for a 36" picket out of half square with tenons on the end.  My basic setup is my forge is in a corner with a pass thru for long iron to go thru. There is a roller stand beyond. In the front I have the required, by the job, number of roller stands depending on the job.. Now I can easily move my long iron fore and aft to get my proper heat. I use a firepot that is ~ 14" long and can get a pretty constant heat over about 12". To get a longer heat I need to move my iron back and forth. 

I don't use a thermometer in my shop, it's redundant. I use the color of the iron to tell me whats going on. I don't even need the numbers. So how do you do this when you are in the black heat range and applying a hot oil finish? Its still visual and smoke has nothing to do with it. As I said above:

1: when it smokes AND your iron is grey, its too hot

2: when your iron smokes AND your iron is that nice matte black, its right on

3:when your iron smokes AND your iron looks wet, you are too cold. 

So the looks of your iron still, in the black heat range, tells the story. Thus, any other tool is not needed. This is step one to a constant matte black hot oil finish.

Now lets look at a constant heat a little differently. Being able to get a constant heat over a given length is a very important step in fire control. But its not the end all. Once you can do this, you need to learn how to get a controlled varied heat over a given length.  This is the critical part for a good finish. The given length depends on your skill level. An 18" heat is simple and 2'-3' or longer is possible. The cooling of your work really is what determines how long of a heat you can take. 

When anyone new comes into my shop I tell them to use the back of your hand to check temp before you pick it up. It will keep you from getting burnt. If you do this with your long iron then when you pull it twards you, with experience, you will get a pretty good idea of its temp for a good finish. This takes experience so start doing it and make it a habit.

On the first 18" heat, i want a constant heat along this length. I shoot for right on to too hot. I don't use a corner of my rag to check temp in one spot,,, or how smoky it is, ,,, I use my rag and oil the whole 18+ inches. If its too hot, wipe her again until you get the finish color you want. If I used a thermometer, by the time I dealt with it, the iron will be cooler and I prolly won't get a full 18" finished section. Thus wasted time. 

The rest of the heats are done a little different. I don't want a constant 18" heat, I want a tapered heat, for lack of better words, and I want it the hottest near me, not the finished section. The hotter you are twards the finished section, the more finish you lose and have no control over. This transition is the area where your finish becomes mottled, not consistent. As the heat travels twards the finished section, watch it carefully and you will see it go to grey and the grey will get longer as more heat travels down twards the finished section. You will also notice an area that is transitioning from black to grey. Its pretty subtle, but its there. Now pull your iron out of the fire and apply your finish so that it overlaps where your old finish ended and keep wiping it on until the end near you no longer is hot enough and it looks wet. 

Repeat 18" at a time til done. Now clean the piece with alcohol and give it a light buff with a carnuba based car/furniture polish and you will have a nice consistent matte black finish. 

 

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Thank you for the explanation.

Please add the type of heat source you are using. 

What type of oil or oil mix you are using, and the source volume of that oil or oil mix you can draw from. (ounces, quarts, gallons, etc.)  

 

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Good point, Glen. My heat source is my coal forge.  I use boiled linseed oil and turps and beeswax. My mix is 50/50 linseed oil, turps and an egg or so sized piece of beeswax. I use a quart of both. I don't think the mix ratio makes a difference to the final look, just the consistency of what ya got. Add more beeswax to make a paste. I like it a liquid. 

I put it all in a 1 gal paint can that has a lid and a bale. This goes onto the top of my coal fire. Use a gentle blast and keep the temp low. If it flashes, and it will, don't worry, just put the lid on and use your poker to move it off the fire. Then put it back on the fire and stir til the beeswax is melted. I then put it back into the two quart cans. The small openings keep evaporation of the turps from happening when not being used and its easy to add the needed mix to a rag. Two quarts done this way last a long time with very little waste.  

Heres what I think happens with this mix. Linseed oil of any type is thick and takes a long time to cool, even when applied hot. The turps thins it out and enhances drying, especially when applied hot. 

The beeswax serves another main purpose. It has the ability to quickly pick up body heat and creates the effect that the iron you touch is warm, not cold. Its a mental thing and we expect the iron to be cold. Sub consciously, and often consciously, we are surprised that the iron is warm. I use beeswax to create this effect specifically. Not to mention you can buff it to get a little iron brightwork on the surface and a nice polished look. 

When I'm done with this phase of my finish, I clean it with denatured alcohol and rub in a light coat of a carnuba based furniture/ car polish and buff it as well. I use alcohol, not mineral spirits. The latter seems to leave a film on the work. So when done, your iron is a nice matte black with a few bright surface highlights, if you choose that is warm to the touch and smells really good.  Usually my rags don't last long enough to be a safety issue,,, just be aware of their potential for spontaneous combustion. Rags are cheap.

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Thank you for the follow up explanation.  

The smaller the graduation on the scale, (ml vs quarts) and larger the quantity of the final mix batch, (gallons vs ounces)  the the more consistent and useful the mix.  Once mixed, storing in reasonable sized containers just makes sense.  

 

Given your measurements, provides a reason to go to the shop and mix up a test batch, to see how it works here.  Thank You.

 

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