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.
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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I just power washed my retaining wall and want to treat it with BLO. I was planning on thinning it with mineral spirits to help the drying time. I live in NJ and was wondering if BLO would be a good application for this project. Thanks
I think it could be a good project for BLO.
Hello, I am a new wood worker, and I have an unfinished piece of furniture I want to work on. the problem is, I don’t have a shop to do it in.
I was planning on doing it on my back deck instead and just bringing it inside with me after I gave it some time outside in the air.
Is this a safe plan? I am going to use BLO and then add a few coats of a water based varnish I bought. The rags will be left on the clothes line to dry out.
Thanks for your time.
Sounds like a good plan to me.
We just made some exterior barn doors in California. We didn’t seal them right away because of low temperatures and they warped a bit. We got them back to straight, then used BLO instead of regular sealer to nurish the wood. Should we, or can we seal them with a polyurethane now or do we need to wait a bit? Guys at Home Depot said we have to wait a year for some reason.
Usually after BLO it just needs about 72 hrs before sealing. If you used pressure treated wood then it does need about 6 months to 1 year to dry out before sealing.
Hi,
First can I say if you respond please assume that I don’t know anything at all.
I am doing a raised Garden Bed and I live where Humidity is pretty high (Alabama).
The total planting area will be 260 sqft
I want to use Pine because it is available in the sizes that I need and the cost is much more doable for the size.
Will BLO protect Pine? Is it safe for the ground contact?
I want to protect the wood so it lasts a few years but I don’t want to do anything that will harm the soil. Any suggestions will be greatly appreciated.
Linseed oil won’t harm the soil but there really isn’t any wood other than pressure treated wood that will survive for long contact with the ground. I don’t know if pressure treated is safe for gardening but I would think it is.
PT wood is perfectly safe for veggie beds.
However the sawdust is not so safe. Use a mask when cutting it, sweep up the sawdust and dispose of safely. Do not leave chips and sawdust lying around. Otherwise it is safe – the wood doesn’t leach significantly even after decades and even if it did, plants don’t take it up – so edibles are safe.
For my for two cents worth, I used pressure treated pine and it is still going strong after 19 years. I live in San Antonio, TX. I didn’t do a thing to it but fill with dirt and plant my vegetables, etc. By the way, I am seeing this blog for the first time because I am using BLO on a project.
The chemicals in pressure treated wood will leach into the soil and make any food grown there unsafe to consume. The wood to use in garden beds would be cedar as it is naturally rot resistant.
BLO Contains Cobalt and Manganese metals to help with the drying of the BLO. You will need to determine if these are safe for consumption…
Can’t you put a mildicide in the BLO to prevent mildew? I plan to soak feshly machined/assembled windows sashes (Vert grain Douglass fir, that I make myself) in turpentine thinned BLO in a very shallow “tank” to achieve the penetration shown in your photo above. Seems to me a mildicide would solve the mildew tendency. Of course the exterior of the sashes will be painted, but the interior spar varnished.
If you plan to paint the exterior then adding mildewcide to the finish paint should be more than sufficient.
I am looking to finish the handle of a new axe. I was thinking about applying a coat or two of mahogany colored stain to the near-white hickory handle but am worried about the final texture. Obviously with axe handles you do not want a finish too slick, or something like a varnish which is too tacky. What would work best? BLO, stain, or something else? I want a bit of color and protection without loosing the texture of the wood.
I would stain the color you want then do a few coats of BLO for extra protection.
In the USMC (before the M-16 plastic stocks) we cleaned our M-14 rifles and coated the wood stocks with linseed oil. This was issued to us at the armory. I never had a problem with sticky, slippery wood stocks in any way. Rifle inspections, rifle ranges, etc., the wood stocks looked good and were protected very well. We cleaned our weapons weekly if not more often. I have never had a problem using linseed oil, ever.
A handyman I used helped me disassemble an old Lutyen bench. We sanded all pieces, reassembled it and coated it with boiled linseed oil. It has turned black over the course of the fall and winter. I live across the bay from Mobile, AL in Spanish Fort where it is very humid. I just saw your posts about not using the boiled linseed oil in high humidity areas. What are your suggestions to get the mildew off and add a protective finish?
Jomax cleaner is excellent at removing mildew. If the piece is outside then I would use a Sikkens stain for protection or something similar.
Tx Scott . Sikkens stain is enough or should I finish with tung oil … ? For outside , snowy weather .
Ting oil is another good option too. But it will take quite a few coats.
But after the stain or even without (except for putting an extra character to the piece)? I thought of diluting the first coating with mineral spirit , than 3 coats tung oil …
Best regards
Thanks so much for the suggestions. I will get the mildew cleaned off and try a stain or tung oil.
I am new to the use of blo, so before using it, i would like to check the advisability of using it on my kitchen cupboards, including the ones above the stove. I would like to also use it on a teek wood dining room table, and an oak bedroom suite. Unfortunately, I am such a novice that I am not even certain if there is any kind of sealer or shellac on any of these. So far, I have just been cleaning with murphys oil, orange glow, amish polish and similar products. I am wondering if blo would be a better more effective choice for the job. Thank you for your most valued opinion
Would BLO be a good finish on a cedar table we just made? And if so, can we put Spar Varnish on the top of it? We’ve seen a lot of instances where people say BLO turns their wood black, and we don’t want this to happen. Any advice?
We want to use cedar wood on our walls on a rec room above our garage. The room will have temperature changes cold winter and hot in summer , I’m a little concerned about the mold issue? What do you think? Thank you for your advice .
Hi Scott I used BLO on a cedar live edge bar top, what would be the best finish application. I was thinking of using either a oil based polyurethane or some type of epoxy finish. What would you do?
Hi Scott! Question…We just picked up our raw hickory butcher block island top from our cabinet maker friend. We decided to go with BLO to start but need a bit more protection so asking your thoughts on the final coat. We are thinking about using your beaswax mixture as the final coat or liquid carnuba wax (the kind with no additives) What would you use? My husband is contractor but using BLO is new to him. He wants to keep in “sandable” so he can re-sand in the future. Thank you so much for any advise!
If you are planning to use the butcher block for any kind of food prep then the only option you really have is mineral oil. If you aren’t using for food prep directly on the surface then I would lean toward the beeswax mixture or a combo of even parts BLO, Mineral spirits, and polyurethane as a wiping varnish. With a few coats this generates an even harder finish than the beeswax.
Indeed!
Hi , sorry to jump in on this but I would like some advice! I have recently used BLO to revamp a pine corner unit. It looks fantastic but I’ve made a mistake! I had to drill out some old wood filler which was too light and have started to refill but it’s stripping the colour and oil 🙁 I’ve got to finish now but will the BLO need to be reapplied to the whole unit or can I get away with patching and blending where the wood filler is? And will this work? Any advice would be much appreciated 🙂 Am so annoyed with myself, I really don’t know what I was thinking leaving the filler til last! Doh! Many Thanks
Would BLO be a good choice for refinishing a wooden outdoor swing? We live in the Houston area where the humidity is high in the summer months. If it is not a good choice what would you recommend? Thanks
Outdoor wood is tough because it will need refreshing almost annually. BLO should be a good choice, just do a few coats initially and then a light sanding and a refresher coat once a year or so.
Teak oil is fantastic for annular treatments of wood, especially if it is subdued to humid climates. Hope this helps.
Hi Scott re-doing a 100 year old stock wagon just got the wooden axels back from the amish would the blo be a great treatment for the new axels made out of white oak the wagon will spend most of it’s time out in the elements in the Midwest thanks for the advice
I would use a mixture of BLO, turpentine and beeswax for some added protection and do a few coats at that.
Scott-what proportions of each? Is there a “recipe”? Thank you!!
1 part of each.
Can you get BLO from Home Depot, Lowes or Menards? Sherwin Williams? I would like to use on a 2 tear old weathered cedar fence that has not been treated. can it be sprayed on?
Should be at all those places and the local hardware stores too.
I live in LOG HOME and above the tub is wood. Do I just apply BLO to bring back the color and remove the water spots? Will I have to apply anything over the BLO
Vicki, I would probably use a mix of BLO, turpentine and beeswax. Shave small pieces of the wax into the turpentine and let it dissolve overnight. Then add the BLO and apply to the wood wiping off the excess. This will give the wood even more protection against water.
Thank you Scott . Question: for indoor ,on a new piece of furniture , to protect it a bit from water , would it be better than shellac?
Tx for sharing your skills.
Happy new year of health and passions.
It’s pretty comparable to shellac in my opinion.
Thank you Scott ! One last question : do you use low cov or odourless turpentine? I am thinking of replacing the with lavender distillate or something else. I live in a cold
Region and do not have the luxury to do my work outside or under a full ventilated room.
I haven’t found an odorless turpentine but yes the smell is pretty tough even with ventilation. I have never used lavender distillate but I’ll have to look into it. I have found that the more expensive and purer turpentine don’t smell nearly as harsh as the cheap stuff though.
I agree for the expensive turpentine. Much less odour . Will try it out. I am also looking for a higher quality BLO (still for COV and odour).
Best regards
Try ALBACK BLO. Some very pure stuff!
Cheers! Great: i do know there products just forgot about them! old age…!
Tx again!
My wife and I have a butternut live edge slab for a bar table. We want something to bring out the details in the wood. We also want a high gloss finish, so we were thinking of going with an epoxy on top. Is it possible to do the BLO as the first layer to bring out the details in the wood, and then finishing it off with epoxy on top?
It is indeed! Just give the BLO a few days to cure before applying the epoxy.
I have a mahogany side table that i rescued from a skip.. the top is badly cracked on the surface…. it looks like deep wrinkles..???? can it be repaired…
We rented a sander and sanded our beautiful “distressed” 50+ year old hardwood floors. They looked very distressed and stains/scratches/ marks, but we loved them that way and chose to use boiled linseed oil because we could maintain it in spots as needed. It turned out beautiful after three coats. Then like big dummies we got insecure that the BLO wasn’t a sufficient sealer and added Johnson Minwax with a rented buffer. Now they look like crap. How can we get the oil off and is the BLO alone, sufficient sealant for our floors? We understand that using BLO means committing to maintenance. The ability to spot treat problems with BLO was a great appeal to us. We’re in a state of panic now. 🙁
Stripping the wax will require mineral spirits and some serious scrubbing.
Hi, I was planning to use a combination of linseed oil and tar. I’ve found various recipes but what concerns me is the mixing it self. There seems to be vague instructions regarding the mixing but they do mention heat. I’d rather not blow up my kitchen so if you have any advice on this I’d greatly appreciate it.
Thanks for doing this awsome page.
Never used that combination before, so I can’t say one way or the other.