[TheForge] Other thoughts on: oil/wax finish, blackened steel
Kim George
klgeorge at kent.edu
Sun Oct 24 23:18:12 EDT 2010
On 10/24/10, Cheryl Brimson <cbrimson at me.com> wrote:
> Bruce:
>
> I agree that you would not want to use linseed oil on anything that will
> come into contact with food, but it does make for an easy to use renewable
> finish, if it wears off. If being food safe is the main criteria for
> finishing the piece I use either the olive oil from the kitchen that I cook
> with, or bowl turner's wax, which is primarily beeswax blended with
> paraffin. I keep a tub of it around for treating the wood bowls we have and
> the cutting boards. If you want to be picky about it, I would argue that
> using metal scale as a component of your finish for something that will come
> into contact with foods not a really great idea either. Low carbon A36
> steel used for most general smithing contains not only iron, but trace
> amounts of carbon, manganese, silicon and phosphorous in the form of oxygen
> free copper. Other alloys contain chromium, nickel, tungsten, vanadium and
> other heavy metals. Like most blacksmiths today, I rely by both examples of
> other smiths and by research
> into current and past practices. In my experience, you use the process
> that suits what you want to achieve, and don't try and use what is not
> appropriate for the particular job at hand. A lot of patination processes
> do use particularly hazardous ingredients (arsenic, copper sulfate, chromium
> oxide, sulfuric acid, just to mention a few) and you have to be extremely
> careful when using them or you can injure your health irreparably. They do
> have their place however, as a means of obtaining a particular look, and
> should not be ignored.
>
> I personally do not forge much in the way of food related metal items. Most
> of what I make falls under the heading of small artistic items or tools. A
> lot of what I finish has to be treated so that it will not rust readily and
> what I have been making for outside applications gets treated with Permatex
> 79DA Rust Treatment, which contains phosphoric acid. I use a wire brush and
> then give the metal three coats while it is still warm off the forge. I let
> the warm (several hundred degrees) steel bake the first coat into the metal
> and when it dries, and place it off to the side on the forge table to keep
> it warm (not hot) and then give it two more coats. If it is necessary for
> the steel patina to show, I then spray it with a clear acrylic sealer. If
> it is going to be left outside, I give it a couple of coats of a good satin
> finish black enamel.
>
> Regards,
> John
>
>
>
>
>
> On Oct 24, 2010, at 8:40 AM, Bruce Freeman wrote:
>
>> As noted in above replies, Japan drier does contain metals, possibly
>> including cobalt. See the Wikipedia article or MSDS sheet (for a
>> particular product) for details. I cannot comment on Brimson's
>> assertions about the degree of hazard these metals pose, as I am a
>> chemist, not a toxicologist, but, it is a given that one does not use
>> "boiled linseed oil" (containing Japan-type driers) on food-contact
>> articles.
>>
>> In the latter regard, let me repeat what I've said many times on this
>> forum: Linseed oil is not a whit better (and it is a LOT more
>> expensive) than any other polyunsaturated oil when it comes to HOT
>> finishing an iron article. Develop the scale on your piece by heating
>> to red and cooling to black. Apply polyunsaturated (cooking or salad)
>> oil when the iron is hot enough to smoke the oil a little, but not a
>> lot. Or, apply a thin coating of the oil to cold, black iron, and
>> bake at 350*F-400*F for an hour. A very nice, shiny black finish
>> results. This is exactly the procedure used for "seasoning" cast iron
>> cookware. It provides some protection from rusting, but will not last
>> long outdoors. What it is, really, is a dark brown dried oil over a
>> black scale. If you put an oil coat on shiny steel, it will look dark
>> brown (which usually is not what you want).
>>
>> So, what I proposed in an earlier post is an experiment I've yet to
>> try myself: Add firescale as pigment to the oil and apply it hot.
>> Carbon black would work for sure as such a pigment, and is suitable
>> for stove blacking (which is mostly carbon black of one sort or
>> another), but might leave an undesirable "marking" surface to some
>> objects. Fire scale is MUCH harder and less likely to mark. But this
>> idea is yet untested.
>>
>> By the way, I consider the key ingredients of stove blacking to be
>> pigment (carbon) and vehicle (oil). Turpentine is to thin the mix,
>> and is irrelevant and undesirable if it is to be applied hot. Waxes
>> might provide a harder surface, or a shinier one, but I doubt it --
>> the baked oil is fairly impervious and quite shiny. Think "dried oil
>> paint" to get the image.
>>
>> And as long as it is understood that polyunsaturated oil must be baked
>> to set properly, then there's no need at all for Japan drier in the
>> mix.
>>
>> Another aside -- Carbon compounds themselves can be quite toxic, and
>> "carbon" from unknown sources may contain oxygen and nitrogen in its
>> chemical constituents (to say nothing of outright contaminants) that
>> increase the likelihood of toxicity. Pure graphitic carbon is safe
>> because your body would never absorb it, but a black compound could
>> contain anything and probably does. (Lampblack, for example, is a
>> suspect carcinogen.) If you really wanted to assure the safety of an
>> unknown carbon black material, you'd have to take some considerable
>> trouble with it.
>>
>> Activated (baked) charcoal is probably the safest by far, as its
>> origin is known and the activation process drives off most of the
>> small molecules. (Activated charcoal is sold at the drug store as an
>> antiflatulent, and is often used to absorb other ingested poisons.)
>> Activated charcoal is the only "black" I would suggest you ever add to
>> anything that will be in contact with food. There may be other safe
>> "blacks", but I don't know them. All this worry is probably
>> excessive, but since the potential toxins are so easy to avoid, you
>> might as well know about them.
>>
>> On Sun, Oct 24, 2010 at 12:05 AM, Cheryl Brimson <cbrimson at me.com> wrote:
>>> If you have any questions about toxicity, do what I've done for years,
>>> check the manufacturer's MSDS sheet. All products, especially
>>> manufactured chemicals, have to be able to show what active ingredients
>>> and physical/physiological characteristics they possess. I looked up the
>>> MSDS for Dynamic Mfg.'s Japan Dryer and Boiled Linseed Oil, and you have
>>> more toxic products in either spray paint/polyeurethane varnish or paint
>>> remover. I have known a few people who suffered from acute sensitivity
>>> to cobalt from grinding carbide tool components in progressive dies, but
>>> that degree of sensitivity is rare. The fumes from using arc welding rod
>>> or the scale you wire brush off forged steel is probably more harmful; as
>>> is the dust from the coal or coke used to forge with. The key is to use
>>> a mask to contain the dust and to have adequate ventilation. Use gloves
>>> to protect your skin from contact dermatitis and you are probably fine.
>>> FYI dryers or accelerants for oil based finish pro
> duc
>>> ts generally do not contain "solids" but are "thinners" such as gum
>>> turpentine or isopropyl (denatured) alcohol. All of which is fine,
>>> unless you are going to try to drink the stuff. Keep a bottle of Scotch
>>> or Captain Morgan on hand for that.
>>>
>>>
>>>
>>>
>>> On Oct 23, 2010, at 10:20 PM, Mike Spencer wrote:
>>>
>>>>
>>>>> ...I've been warned that the dryers in "boiled linseed oil" and
>>>>> japan dryers are capable of giving you heavy metals poisoning...
>>>>
>>>> I think (but can't immediately confirm) that "Japan drier" has become
>>>> a generic term for several kids of drier. Cobalt is used in several
>>>> brands of driers. In addition I've seen an allegation that "boiled"
>>>> linseed oil contains "arsenic, beryllium, chromium, cadmium and
>>>> nickel" as drier constituents. Bleee.
>>>>
>>>> Years ago, a smith here called the makers of a brand of boiled linseed
>>>> oil sold here and asked about using it on food prep utensils. The
>>>> company rep emphatically urged him not to do that, but to use "raw"
>>>> linseed oil. The rep confirmed that "boiled" isn't boiled but has
>>>> driers added.
>>>>
>>>> So I just stay away from "boiled" linseed. For a railing or exterior
>>>> paint it's probably fine but why mess around?
>>>>
>>>> - Mike
>>>>
>>>> --
>>>> Michael Spencer Nova Scotia, Canada .~.
>>>> /V\
>>>> mspencer at tallships.ca /( )\
>>>> http://home.tallships.ca/mspencer/ ^^-^^
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>>
>>
>>
>> --
>> Bruce
>> NJ
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--
Kim George
"Why for you try to bury me in cold,cold ground?"
Taz
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