Boiled Linseed Oil, Painted Cloth and other toxic discussions
I've received several questions regarding my experiments in period paints of late and thought I might drone on about the subject a bit.
Several years years ago when I made my first painted haversack I became intrigued by the paint that was used to coat it and started researching. A few years ago I came across a period description of how painted cloth, or "American Cloth" as it was known in Europe, was manufactured. There was indeed a race to develop cheaper alternatives to the patented rubber sheeting of the era and particularly intriguing to me was the descriptions of the variety of types and styles of cloth that was available as different entrepreneurs entered the fray. Also of interest was the levels of quality that was being reached in American factories. I was able to obtain a couple of samples of early american painted cloth that had been deaccessioned from a museum's collection and was amazed how fine its quality it truly was. What started as a journey into stitch counting has very much become a study of American capitalism and Yankee ingenuity. The painted cloth and rubber coated fabric industry leads eventually to vinyl, modern oil cloth, naugahyde, pleather, while its companion industries move from rubber and gutta percha to Bakelite and modern plastics. A surprising number of modern corporations can trace their lineage to the manufacturers and inventors of the 19th century. The journey has altered my perspective from seeing the plastic , polyester, and synthetic nature of our modern era as merely a sign of what we have lost to recognize that it is no less than the pinnacle of what the industrialists and dreamers of the 19th century were reaching towards. An interesting journey for me that started with the simple desire to apply period oil paint to cotton and linen cloth. All I can say is ain't research fun. :-)
Anyways, what I meant to write about when I started this thread was a few of the questions I've received and to share some of the lessons and resources I've discovered the last few years while experimenting with painted cloth.
One of the common questions I get relates to the toxicity of period paint recipes especially if someone has been to the MB & S page with the MSDS sheet on modern "boiled linseed oil". The problem here is that what is being sold in hardware stores as "boiled linseed oil" truly isn't what it claims but rather polymerized linseed oil, a combination of raw linseed oil, petroleum-based solvent and metallic dryers. The additives help polymerized linseed oil dry much faster than the traditional formula of pure linseed oil heated to 225° F.
It isn't the linseed oil that is toxic but the chemical additives. Pure linseed oil, also known as flax oil is actually food grade and is even ingested as a dietary supplement. Heating Linseed oil costs more than simply mixing in chemicals and since most consumers don't know the difference the polymerized linseed oil is what most hardware stores stock.
Drying and Curing
Pure boiled linseed oil can take days and even weeks to dry which is why chemical dryers are frequently added. The adding of chemical dryers to speed the curing time is not new and many period recipes called for Litharge (lead monoxide), Sulphate of Zinc, and white lead to be added to paint. The toxicity of these early driers (along with some period pigment recipes) is what gives period paint its toxicity. Many modern driers such as Cobalt drier, lead napthenate, Japan Drier, or liquin may not be as dangerous as lead but still have toxicity risks at various levels and great care should be taken when using them. Chemical dryers can also lead to a finish that is prone to cracking and crazing over time.
Unlike other paints, oil paint doesn't dry through the evaporation of liquid contained in it but rather through a process of oxidation and polymerization. This process is sped along by circulating air and elevated temperatures. Without knowing the chemistry early experimenters figured this out and descriptions of the early manufacturing process had painted cloth hung high up in the rafters to help speed the drying process. Quick curing is one of the advantages I have is living in a desert with 0% humidity and 115° temperatures in the shade. However, even in my environment I've had experiments with some paint formulas that I had to scrap because they remained tacky still after several months. Paying attention to the temperature and the humidity levels before starting a painted cloth project can decrease your grief later. Regardless, of your environment though, the key is patience and testing.
As most everyone should know oily rags pose a very real fire danger and need to be disposed of properly. Spontaneous combustion can occur as a result of the heat generated from the oxidation process as the oil dries if it is not allowed to vent and release the generated heat properly. This isn't only true of Boiled Linseed Oil and other oil paints but even olive oil and vegetable oil soaked rags can lead to combustion. The key is to let the painted cloth fully cure while allowing the heat generated from the drying process to dissipate. Rather than wading up your newly painted oil cloth and tossing it into a closet or shed, hang it on a line where plenty of air can circulate around it until it is fully cured. Unfortunately such things require time and space, something that equals money in modern manufacturing.
Tastes and odor
Pure boiled linseed oil actually has a rather pleasant oder compared to the chemical smell of polymerized linseed oil. I've used ration bags and haversacks painted in period paints for several years now and never noticed any flavor imparted to my food. Again the key is patience and letting your work cure before using. Once it has thoroughly dried it can be very difficult for even the most discerning nose to notice any smell whatsoever.
Good news from environmentalists and artists
Happily for our purposes there is a great deal of cooperation between environmentalists who want less toxic, natural paints and artists who have a long history of putting oil paint on canvas. What started on a small scale with the concern of artists about the toxicity of the paints they use has begun to develop into a full fledged industry as mere research is done on the toxicity of fumes associated with new home construction.
As environmentalists look for ways to move away from the petrochemical paints they have moved back towards more more environmentally friendly paints made from organic and natural ingredients. When reading the descriptions of these "earth friendly" paints it is remarkable how closely many of them match period paints (of course without the litharg and other period toxic dryers). Much like in the 1860 there is again a great deal of testing and development being done on paints made from natural ingredients. Several companies are even commercially producing paints that match period recipes. Watching this new industry develop is enough to make one wonder if there is a larger market outside our hobby for raingear made from hemp fiber and natural paints? ;-)
Anyways, my goal in starting this discussion is not to renew the age old arguments of the appropriateness and safety of latex paint on period haversacks, knapsacks, and ground sheets but to hopefully give a little boost to the next round of folks who decide to experiment with period painted cloth. It is quite possible to experiment with period paint recipes and methods while also being aware of and addressing health concerns. That said, these resources may be of use to those of you out there working with the medium of painted cloth.
Tried and True Wood Finishes
Solvent Free Paint
The manufacturing of Leather cloth
THe Manufacturing Process
Linseed Oil - Its Uses and Limitations
Non-toxic Paint 101
About Oil Mediums
The Secret of Oil Painting Without Solvents
Drying Oils or Mediums Used in Oil Painting
Oxidation of Linseed oil
Spontaneous Combustion Tendency of Household Chemicals
Hazard Data Sheet - Using Artist's Paints
Make Your Own Safe Non-Toxic Paints
And of course you can always use the AC search function to locate the many discussions on related topics. Here too patience and trial and error are the keys to success.
Last edited by AZReenactor; 07-18-2010 at 01:59 PM.
Troy Groves "AZReenactor"
1st California Infantry Volunteers, Co. C
So, you think that scrap in the East is rough, do you?
Ever consider what it means to be captured by Apaches?