For me it is CA/BLO because I put the CA on the wood first and then the Boiled Linseed Oil (BLO). I have never said it any other way. Anyone who has read anything other than that into anything I have ever said was not paying attention.
My reasoning for the CA first is that the results are more predictible and there is less risk of failure. That makes it easier for me to use, and easier to teach others how to use the finish. Let me explain why I say this.
Any oil will accent the grain of the wood because oil changes the wood color and it penetrates deeper into end-grain than flat-grain. Since highly figured wood is a combination of both end and flat grains, this color difference will accent the grain pattern. When this color variation is a good thing, we call it "enhancement". When it isn't, we call it "blotchy".
The thing that most people miss when they put the BLO on first is that the oil HAS to be cured BEFORE anything other than more oil can be put on top of it. Cured" means no liquid oil on the surface. If the oil HASN'T cured, the new finish WILL be compromised because its adhesion to the surface has been compromise. That is true for any finishing oil or product that contains a finishing oil.
We can sometimes get away with the oil not curing before we put on the CA finish because the pen is small and round. What we have is a tube of finish that is wrapped around the wood, but with poor if any adhesion. It may look good in the short term, but it will peal or flake off over time or if it is ever scratched sufficiently to break the surface.
There are two (2) ways to cure the BLO, time and/or heat. Finishing oils cure by polymerization of the smaller liquid molecules into larger solid molecules. It has made the transition from liquid oil to a solid finish. That reauires heat. It either has to generate its own heat or we can provide it. Left to its own at room temperature, it will be a slow precess that can take from overnight to 2 or 3 days. Adding heat can shorten the cure time to minutes, and friction heat is the best kind because it provides the heat while the applicator is removing the excess oil from the surface.
Eagle has discovered that basic fact about using finishing oils - the hotter they get, the faster they cure; and once cured, you can put lacquer, shellac, CA glue, and even a waterborne over it. None of these other finishes will stick to a liquid oil.
There is always the question of how much heat and how hot is "hot"?? Hot is finger burning hot. It may be overkill, but you are getting enough heat on the surface if you are burning your fingers through 8 layers of paper towel. "Finger burning hot" is only about 130F for most of us. The 8 layers of insulation insures that when the top surface is 130F, it is getting close to 175F at the surface. That is the kind of heat I am talking about. Anything less and the BLO isn't cured. It follows that the wood has to cool to room temperature before any other finish is put on top of it.
The downside to doing it this way is that some wood cannot handle those temperatures and it will shrink, crack, change shape to no longer being round, and a few other things that can ruin a pen. Another cause for out-of-round because some grain directions expand more for the heat than others, and it doesn't always return to the same place when it cools.
There is always the risk that, no matter what we did, it didn't get cured enough because some wood is more porous than others and will have a deep penetration of a lot of oil that may or may not get fully cured.
Why the BLO on top of the CA glue??
Besides getting around the issue of having any liquid oil under the CA because it was given neither the time nor the heat to cure, putting the BLO on top does three (3) things.
1. It provides a lubricant that allows the CA to be spread to a uniform film. Any oil will do this.
2. It provides and accelerator for a faster cure of the CA, and the oxidizers that are added to the Raw Linseed Oil to make it into what we call "Boiled" make it better as an accelerator than other oils. That acceleration is why it works better with a slow setting CA glue, and the s-l-o-w-e-r the better.
3. This is the complicated one. It allows some small portion of the BLO to migrate through the CA finish and get to the wood where any differences in penetration will cause the grain to be accented. Now comes the complex chemical reaction. CA glue gets hot as it cures, and that heat will also cause the cure of the BLO that has gotten under it. As the CA cures it seals the cured BLO under it, and forms a hard finish on the wood.
Again, there is a downside, and this time there are two (2).
In doing this, some of the BLO has been trapped in the CA glue, making it take longer to fully cure. "Fully" means cured to where it can be polished without damage by a buffing wheel. What we usually call "cured" is only cured enough to handle. I would leave it overnight before buffing.
The other downside is that some of the BLO will be trapped in the CA film on the surface and it will not always have the same gloss as a pure CA finish that has used no oil. Waiting until the next day and sanding through 12,000 Micro-Mesh, buffing with White Diamond, or using a plastic polish will solve this problem.
We all need to try it both ways to determine for ourselves whether CA/BLO or BLO/CA is the better way to do it. My observation over several years of using both CA and BLO is that there is no difference in the final result. It doesn't matter which goes on the wood first, PROVIDED THAT the BLO has FULLY CURED if it is put down first. I chose to use the CA first because there is no risk that the BLO was not cured.
My further observation is that either way will accent the grain more than if the BLO were not used at all.
There are oil based finishing products on the market that cure faster than Boiled Linseed Oil because they have had enough drying agents added to them that they generate their own heat and make the polymerization reaction happen faster. They are not magic. They just do the same thing faster with the addition of chemicals to the oil. I will leave it to someone else to determine whether they are better than Boiled Linseed Oil. For myself, I will continue to use BLO because it works, it is predictable, it is fast enough for me, and it is cheap and available.
My reasoning for the CA first is that the results are more predictible and there is less risk of failure. That makes it easier for me to use, and easier to teach others how to use the finish. Let me explain why I say this.
Any oil will accent the grain of the wood because oil changes the wood color and it penetrates deeper into end-grain than flat-grain. Since highly figured wood is a combination of both end and flat grains, this color difference will accent the grain pattern. When this color variation is a good thing, we call it "enhancement". When it isn't, we call it "blotchy".
The thing that most people miss when they put the BLO on first is that the oil HAS to be cured BEFORE anything other than more oil can be put on top of it. Cured" means no liquid oil on the surface. If the oil HASN'T cured, the new finish WILL be compromised because its adhesion to the surface has been compromise. That is true for any finishing oil or product that contains a finishing oil.
We can sometimes get away with the oil not curing before we put on the CA finish because the pen is small and round. What we have is a tube of finish that is wrapped around the wood, but with poor if any adhesion. It may look good in the short term, but it will peal or flake off over time or if it is ever scratched sufficiently to break the surface.
There are two (2) ways to cure the BLO, time and/or heat. Finishing oils cure by polymerization of the smaller liquid molecules into larger solid molecules. It has made the transition from liquid oil to a solid finish. That reauires heat. It either has to generate its own heat or we can provide it. Left to its own at room temperature, it will be a slow precess that can take from overnight to 2 or 3 days. Adding heat can shorten the cure time to minutes, and friction heat is the best kind because it provides the heat while the applicator is removing the excess oil from the surface.
Eagle has discovered that basic fact about using finishing oils - the hotter they get, the faster they cure; and once cured, you can put lacquer, shellac, CA glue, and even a waterborne over it. None of these other finishes will stick to a liquid oil.
There is always the question of how much heat and how hot is "hot"?? Hot is finger burning hot. It may be overkill, but you are getting enough heat on the surface if you are burning your fingers through 8 layers of paper towel. "Finger burning hot" is only about 130F for most of us. The 8 layers of insulation insures that when the top surface is 130F, it is getting close to 175F at the surface. That is the kind of heat I am talking about. Anything less and the BLO isn't cured. It follows that the wood has to cool to room temperature before any other finish is put on top of it.
The downside to doing it this way is that some wood cannot handle those temperatures and it will shrink, crack, change shape to no longer being round, and a few other things that can ruin a pen. Another cause for out-of-round because some grain directions expand more for the heat than others, and it doesn't always return to the same place when it cools.
There is always the risk that, no matter what we did, it didn't get cured enough because some wood is more porous than others and will have a deep penetration of a lot of oil that may or may not get fully cured.
Why the BLO on top of the CA glue??
Besides getting around the issue of having any liquid oil under the CA because it was given neither the time nor the heat to cure, putting the BLO on top does three (3) things.
1. It provides a lubricant that allows the CA to be spread to a uniform film. Any oil will do this.
2. It provides and accelerator for a faster cure of the CA, and the oxidizers that are added to the Raw Linseed Oil to make it into what we call "Boiled" make it better as an accelerator than other oils. That acceleration is why it works better with a slow setting CA glue, and the s-l-o-w-e-r the better.
3. This is the complicated one. It allows some small portion of the BLO to migrate through the CA finish and get to the wood where any differences in penetration will cause the grain to be accented. Now comes the complex chemical reaction. CA glue gets hot as it cures, and that heat will also cause the cure of the BLO that has gotten under it. As the CA cures it seals the cured BLO under it, and forms a hard finish on the wood.
Again, there is a downside, and this time there are two (2).
In doing this, some of the BLO has been trapped in the CA glue, making it take longer to fully cure. "Fully" means cured to where it can be polished without damage by a buffing wheel. What we usually call "cured" is only cured enough to handle. I would leave it overnight before buffing.
The other downside is that some of the BLO will be trapped in the CA film on the surface and it will not always have the same gloss as a pure CA finish that has used no oil. Waiting until the next day and sanding through 12,000 Micro-Mesh, buffing with White Diamond, or using a plastic polish will solve this problem.
We all need to try it both ways to determine for ourselves whether CA/BLO or BLO/CA is the better way to do it. My observation over several years of using both CA and BLO is that there is no difference in the final result. It doesn't matter which goes on the wood first, PROVIDED THAT the BLO has FULLY CURED if it is put down first. I chose to use the CA first because there is no risk that the BLO was not cured.
My further observation is that either way will accent the grain more than if the BLO were not used at all.
There are oil based finishing products on the market that cure faster than Boiled Linseed Oil because they have had enough drying agents added to them that they generate their own heat and make the polymerization reaction happen faster. They are not magic. They just do the same thing faster with the addition of chemicals to the oil. I will leave it to someone else to determine whether they are better than Boiled Linseed Oil. For myself, I will continue to use BLO because it works, it is predictable, it is fast enough for me, and it is cheap and available.
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