Penetration Of Boiled Linseed Oil When Applied To Hickory Wood

Introduction

There is a growing trend of soaking and/or oiling axe and tool handles for extended periods of time. However, very few people have actually tested the penetration of boiled linseed oil on Hickory wood to see how well the oil is actually absorbed.

In this experiment, I will compare the before and after weights to see how much boiled linseed oil is absorbed.

Set Up

To start the experiment I cut five nearly identical pieces of wood. Each piece is three inches long and around 42g in weight. They were sanded with 60 grit sandpaper and soaked at room temperature to ensure optimal oil penetration.

For oil I used straight Boiled Linseed Oil. It’s commonly available, cheap and is the go-to choice for most people.

Number                   Start Weight                 Final Weight                   Soak Time
Control                               44g                                      44g                       Daily Application
#1                                        42g                                      42g                               3 hours
#2                                        40g                                      42g                               24 hours
#3                                        40g                                      42g                               3 days
#4                                        42g                                      48g                               5 days

Results

Control Sample 

For a control sample, I simply wiped down one piece of handle every day for the full five days. This is equivalent to the standard treatment for axe handles since soaking the entire handle isn’t practical.
As you can see there is no penetration line visible and the weight is unchanged.  Considering this is under optimal conditions daily oiling is the least effective method.

Sample #1

Sample one was soaked for 3 hours in a boiled linseed oil bath.  Again, there is no visible penetration line and there was no change in weight.

Sample #2

The second sample was soaked for 24 hours. This time the weight did increase by 2g but there still is no visible penetration line.

Sample #3

Sample three was soaked for 3 days. This time the interior was slightly darker.  Although there is no clear line to judge penetration.  The weight gained was 2g. Identical to sample #2.

Sample #4

For the final sample, I soaked the handle section for 5 days. The weight increased by 6g. To put that into perspective that is roughly a teaspoon of oil that was absorbed into only a three-inch section of handle. The interior color was slightly darkened but not as dark as sample #3.

Conclusion

So what does this all mean?

Unless you’re willing to soak a handle for an extended period of time, under optimal conditions, you really won’t have much oil absorbed into the wood.  With daily oiling being the most unproductive method.

As far as oil penetration is concerned the cell structure of the wood acts to wick the oil and evenly distribute it all the way to the center of the wood.  Which is why there is no clearly defined penetration line in any of the samples.

Is more oil better? That question is beyond the scope of this article, however, more is not always better. There are studies that show once linseed oil polymerizes it causes micro cracks in the woods cell structure and decreases flexural mechanical properties quite significantly. Also, keep in mind linseed oil polymerizes through oxidation.  So only the very surface will actually harden.  Leaving the inside uncured for years. Possibly decades.

In the end, in order to get deep oil penetration, you would have to soak the entire handle for weeks.