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How To: Use Boiled Linseed Oil (Safely)

How To: Use Boiled Linseed Oil (Safely)Boiled Linseed Oil (BLO) is a common item in my shop and in a lot of woodworker’s shops. It is a great oil treatment for woods, leaving a smooth touch on the surface. It revitalizes old dried wood and gives it a new life.

BLO is often mixed with other finishes and was once one of the main ingredients in most paints. There are still companies that make linseed oil paints like Allback if you’re interested.

Boiled Linseed Oil is not actually “boiled” like the name suggests, rather, it is chemically modified to encourage faster drying. Slow drying oils are a good thing, but regular linseed oil can take weeks or even months to fully cure in cold weather and that’s just too stinking long. Boiled Linseed Oil will dry in only a few days give or take depending on weather.

As awesome as this product is for both wood and metal, it has some dangers (specifically flammability) that need to be addressed in order to use it safely. Let’s talk about safety first.

Boiled Linseed Oil Safety

The hard truth is that Boiled Linseed Oil can spontaneously combust if stored or used improperly.

“Why on earth would you use it then?”

Well, gasoline is a lot more flammable than BLO and I don’t hear anyone calling their cars a death trap (except Corvair owners).

Here’s what happens: BLO cures by a chemical reaction with the surrounding oxygen in the air not by evaporation like water based finishes. This reaction generates heat like most chemical reactions. The heat generated can be intense in certain circumstances and can lead to spontaneous combustion.

Larger amounts of BLO create greater heat. Smaller quantities generate less heat.

How to Avoid Fires

  • Always store BLO in metal containers. You can pour it into plastic containers for temporary use, but for long term storage it should be in a metal container.
  • Any rags soaked with BLO should be laid flat on a non-flammable surface away from flammable items until they are completely dry or they can be placed in a metal container with water.

The most common source of BLO fires is from a wadded up rag that has been soaked in BLO. The rag is wadded up and thrown in the trash with wood dust, newspapers or other kindling.

Since it is wadded up, it generates more heat because there is no air to pass over it and cool it. It then heats up to the flash point of the surrounding materials and the fire starts.

Watch this video to see how this happens.
//youtu.be/9yq6VW-c2Ts

Despite this issue, I still believe BLO is a great option for wood and metal. Read below, and you can learn how to safely use Boiled Linseed Oil.

Boiled Linseed Oil & Wood

BLO is a great protectant for wood both indoors and outdoors. It beautifies any wood and, once cured, protects the wood from sun and water damage. It can really reinvigorate old dried out wood and bring it back to a healthy status.

linseed oil penetration
Image Copyright: SolventFreePaint.com

The powerful thing about an oil finish like BLO is its deep penetrating abilities. After application, the wood fibers draw the oil deep inside which protects not just the surface, but the whole piece of wood like in the image here.

Wipe on a couple coats of BLO on furniture, trim, or any bare wood and let it dry until it is no longer tacky (usually 24-72 hrs). The application is as simple as it gets and the results are more than worth the effort, which is why it has been used for hundreds of years by carpenters and refinishers.

Boiled Linseed Oil & Metal

A lesser known use for BLO is to protect metal from oxidation. You can apply a thin coat to non-moving parts and once dry it will protect and beautify the surface. Thick coats can get gummy which is another reason you don’t want to use this in moving parts which get stuck together.

I use it mainly for chisels, screwdrivers, heirloom tools, block planes, and more specifically cast iron tops of my “Big-Boy” tools in the shop like the table saw, mortiser, and band saw.

Sand off the rust and polish the metal with some 0000 steel wool, then wipe on a thin coat of BLO and you’re good to go.

Boiled Linseed Oil has one other thing that can cause concern, especially in humid climates. On exterior surfaces in humid wet climates it has a tendency to mildew. So, before you go coat all your adirondack chairs, test an area for a while and see how it does.

If you do get mildew, it’s not the end of the world as it can be easily cleaned off, but that’s why in Florida I prefer to use it mainly indoors.

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251 thoughts on “How To: Use Boiled Linseed Oil (Safely)

  1. Ive made a canoe paddle will the boiled linseed oil be a good water barrier? And should I stain it before or after oil? Thank you

    1. hope you figured something out by now but if not, I doubt an oil finish will provide sufficient waterproofing. You really want to seal the wood with something like a marine use spar varnish which I think is what most of my wood Sawyer brand paddles are finished with.

    2. Stain first, yes. Linseed is traditional but not the most permanent. But if you use it, reapply every six months. In a set that I made I scorched the well dried wood paddles and then applied BLO. But I continue to reapply each time I put them up for the season.

      1. I agree wholeheartedly with Ezra (surprise … he is an expert) but I have had the same beaver tail paddles for over 40 years and have always used poly. I seldom revarnish more often than every 5-6 years – even the tips are within a hair of ‘like new.’

        I’m 78 and still solo the wilderness rivers every year (thank you God!) I’d like to say that I’m within a hair of new, but time does put a little deterioration around the edges. The legs ain’t what they used to be but I can still haul arse over the portage’s.

  2. What do you think about using BLO on cork flooring with pet urine stains? The stained areas are now clean, but they absorbed the liquid and are now permanently darker than the rest of the floor. Might BLO even out the coloration?

  3. Hi, this is all really useful. My question is can you work with BLO in very cold temperatures? My project has to be worked on in my shed, typically we are experiencing temperatures of zero degrees and lower. Might the BLO react badly?

  4. I’m new at woodworking and this thread has been helpful. I made two containers out of cedar on a wood lathe and finished them in blo. They look terrific but are they safe for storing kitchen utensils in? Giving them as Christmas presents to my daughters and appreciate your advice.

      1. I agree with the above finishing of cooking and kitchen ware. I have used many systems to protect small items. When i need something safe and easily available, I use Olive Oil with good results. Of course it will have to be reapplied a couple of time a year.

      1. I used to participate in a Meet-Up group that went canoeing and kayaking in southern KY. Maybe that’s it? As soon as I have some time I would like to find a wood turning group somewhere close to home.

  5. Just made a dibbler (or dibber) on my lathe. I will apply a coat of BLO soon.
    After it dries, can I also apply a mixture of paraffin & mineral oil (as I do on my cutting boards)?

  6. Hi Scott,

    I live in England and I’m currently renovating a Arts and Crafts Farmhouse. All the doors are original with the steel door latches. These have been painted (and varnished!) over the years. I’d like to stop them without losing all of the patina. I can get the paint off but rust soon gets a grip. Can I finish them in BLO? My concerns are…will it ever fully cure on metal and how often do I need to recount? Can I just apply with a cloth or should I use a brush? Sorry, for the multiple questions but happened upon your blog and I’m hoping BLO might just be the answer I’ve been looking for. Thank you in advance.

    1. BLO definitely works to coat old hardware though it does dry to a soft finish. A couple other options for coating hardware you should check out are Boe-Shield and Penetrol.

      1. Thanks Scott. Both products appear to be available in the UK so I’ll try a little experiment with the two. Very nice blog.

    2. Hey Scott!
      I’ve got a cedar outdoor rocker, and I’ve applied about 3 coats of blo to it. But it soaks it unevenly mostly around knots and entrain.
      Is their sealer i can use after I get tired of applying blo?

  7. Can i use blo on my oxidized garage metal door to freshen it up?if so what should i do first? A vinger wash?

  8. I’m recovering (with canvas) my wood and canvas canoe. I’ve got two coats of blo on the canvas. I’ve mixed in silica sand to fill the warp and woof of the canvas weave. There was sand, saturated with linseed oil left over.

    I had the mix in a plastic pail. I sealed the pail with plastic wrap – and the brush separately.

    Are they safe from self combusting? Thanks.

  9. I am looking for a product to apply to the exterior of our house which is protected by wrap-around porches and is not exposed to sun or much weather. The exterior is a horizontal lap siding made of fir. In the past, we have treated the entire house with good quality, UV protectant transparent stain, and I expect to continue with that in the areas that are exposed to the sun and weather. But even the “natural” colored stains are turning the house darker each time I reapply. Also, I realized that I am spending money on UV protection that I really don’t need for the unexposed areas. And I am looking for more of a natural oiled look. We live in a semi-arid/dry climate (southern Idaho), so mold and mildew in not an issue. Would linseed oil be a good product to use? If so, can it be applied with my airless sprayer? Thnx for any insight.
    Rick

  10. I just got in a 3′ x 8′ Maple butcher block work bench for my shop. Tabletop drill press, vise, some banging, beating and a little mechanical grease. Is BLO an acceptable treatment for this?

    1. Can you use an oil or water based stain to get the color your looking for, then use BLO as a finishing product? I am doing a fence with 2×6 tongue and groove, clear pine. Thanks. If not, what do you recommend?

  11. I have just built my stairs and I have used treated pine on the stair threaders. I plan to use BLO on the threaders as I want to retain the natural look of the grain and wood. Is this the best way of doing this or should I add turps and beeswax to the BLO. Also how many coats of the BLO should I use?

  12. I used BLO on my work bench in my garage. Can I use Polycrylic as a top coat to help protect the top surface, or some other kind of top coat?

  13. I have an old horse drawn plow that I am cleaning. I was thinking of putting linseed oil on the handles. Will this protect the wooden handles from the elements as I was going to sit the plow in my yard?

  14. Hello Scott,

    Thank you for your site. Very helpful!

    Is there a disadvantage of using BLO as finish on floors (interior and exterior)? Should I be concerned about dust collection, stains or other issues?

    Regards,

  15. Our home has 50 year old cork floors. They are faded and worn but we love them and have no desire to replace. How can I use linseed oil to bring Them back to life?

  16. I would like to use the Allback blo on a pressure treated outdoor pavilion. My client wants the wood to stay a light natural wood tone and to NOT turn grey. Provided that the blo is re-applied every few years, will the linseed oil prevent the wood from turning grey?

  17. I’m refinishing an old wooden box chest. There was a strong moldy/mildew smell which I treated with vinegar which didn’t work too well. I then tried bleach and the odor is almost gone. I now want to apply linseed oil and hope whatever odor is still there will be sealed in by the linseed oil. Will this work.

      1. Rubbing with then letting stand on the wood, used coffee grinds help remove odor. Once washed out the coffee smell will dissipate.

    1. If I can put my two cents’ worth in, I have had great success using hydrogen peroxide to kill mold and the smell. It works great and doesn’t leave a smell like bleach does. Also, we had an animal go through a window and bleed out on our museum’s 100+ year old wood floors. Peroxide took that horrible stain right up!

  18. Would BLO be the idea stuff to use to seal a piece of wood before using vinyl as a stencil for acrylic paint?

  19. Hello!

    I’m trying to seal a 4″ deep wood slab to turn it into a cake stand. Would I be able to seal it with just Linseed oil? Or would I need to add a spray epoxy coat afterwards? And if I need to do the spray epoxy, how long should I wait after using the boiled linseed oil?

    Thanks!!!

    1. DO NOT use Boiled Linseed Oil for this purpose. It is toxic. Use either walnut oil or mineral oil – personally I use mineral oil for anything like this. It is cheap, easily available, and soaks in well. Just give it time to soak in and cure.

  20. I read about it being used with metal. I have an old cast iron farm bell. Was thinking about using it on. Any suggestions? Sand with 0000 wool and then coat with BLO?

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