I have always heard that BLO requires about 24 to cure, then several more days for a final cure.
It's been in the 90's the last week.
I applied a heavy coat several days ago onto walnut, then wiped the excess an hour later. Seven days later and the scent of BLO is still very strong and after I handle the pieces, my hands smell strongly of BLO.
Is this normal? Should I panic? How long until this goes away?
In this context "cure" means complete the reaction of oxygen with the oil to crosslink the oil. This reaction generates some volatile stinky products, the smell of curing linseed oil. The stinky compounds are easily detected at very low concentration. How fast this reaction proceeds is strongly dependent on temperature, as well as relative humidity which deactivates the catalyst, and the catalyst concentration the manufacturer added to make it "boiled". (It is not boiled; rather it has catalyst added).
Your question really comes down to, how much does the oil have to cure before it can be over coated with varnish. The issue is bonding of the varnish to the oil coated wood. I don't know the answer but the oil does not have to cure to the extent that there is no oil odor. In my experience most of the curing oil smell would be passed well before 7 days at 90 degrees. I have never had any adhesion problems after about 2-3 days of summer temperatures.
I just finished a mantle for someone that was oiled to add color before spraying with Conversion Varnish. I waited 3 days at about 80 degrees and there was little odor after this time.
Depending on the varnish top coat, the oil will not add any benefit. Always test to see if the oil is beneficial to appearance.
06-04-2022, 08:25 AM (This post was last modified: 06-04-2022, 08:29 AM by CStan.)
Don't do the flood coat cha-cha-cha in heat and humidity. Just pad on a very thin application, let it sit 30 minutes, and buff off. Forget using any kind of brush. Two applications a day over a couple or three days and you should be done.
BLO, Danish oil, and similar products can always be done this way, and you are not going off the reservation in doing so.
Dump all textiles, paper towels, etc. that have BLO on them in a bucket of water, or lay out flat on concrete in the sun.
For the project in front of you now, buff it like hell and/or wait. That's about all you can do.
Do not try to get it off by wiping down with mineral spirits, naptha, DNA, or any other kind of solvent.
(06-04-2022, 06:25 AM)Bill Tindall Wrote: In this context "cure" means complete the reaction of oxygen with the oil to crosslink the oil. This reaction generates some volatile stinky products, the smell of curing linseed oil. The stinky compounds are easily detected at very low concentration. How fast this reaction proceeds is strongly dependent on temperature, as well as relative humidity which deactivates the catalyst, and the catalyst concentration the manufacturer added to make it "boiled". (It is not boiled; rather it has catalyst added).
Very true. I've been known to add some additional Japan Drier to purchased 'BLO' to speed the process. Gunstocks and walnut furniture just look and feel great with a BLO finish, and I'm not a patient guy. The Drier is available at Sherwin Williams stores, and others I'm sure.
(06-04-2022, 08:25 AM)CStan Wrote: Don't do the flood coat cha-cha-cha in heat and humidity. Just pad on a very thin application, let it sit 30 minutes, and buff off. Forget using any kind of brush. Two applications a day over a couple or three days and you should be done.
BLO, Danish oil, and similar products can always be done this way, and you are not going off the reservation in doing so.
Dump all textiles, paper towels, etc. that have BLO on them in a bucket of water, or lay out flat on concrete in the sun.
For the project in front of you now, buff it like hell and/or wait. That's about all you can do.
Do not try to get it off by wiping down with mineral spirits, naptha, DNA, or any other kind of solvent.
I don't understand why several thin applications over days offers any advantage over one flood, followed by a wipe, that offers the wood all the oil it will take. This approach is what I have always used with no problem I have detected. I often heat the wood with a hair drier to thin the oil and penetrate even more. An initial flooding will get more oil in the wood, which could be beneficial for wood knife handles, gun stocks and maybe something else. The polymerization of the first thin coat will retard penetration of subsequent coats, for better or worse.
When I did the mantle I flooded the linseed oil, then wiped off with the usual tee shirt scraps. These were soaked in oil. Curious, I thought I would try to ignite them. I waded them into a baseball sized wad and put them in an open can surrounded by sawdust for additional insulation. Nothing happened. The rags didn't even get warm after an hour or two, or overnight.
Flooding of the mantle put enough oil in the wood that this step became a sealer coat, eliminating the sealer step of the conversion varnish that followed. In this case flooding was beneficial. In two days I sprayed conversion varnish and done.
The curing reaction generates heat. If this heat is generated faster than it dissipates the rag temperature will increase, which will make the cure go faster and the heat build up even more. But that didn't happen in this case. I'm skeptical linseed oil will ever cure fast enough to generate enough heat to ignite. A fast curing varnish could be another story.
Has anyone ever experienced firsthand rags getting even warm from having been used to wipe oil or varnish or paint? If so, what were the conditions?
(06-04-2022, 08:50 PM)®smpr_fi_mac® Wrote: Is there any chance that the opened container being many months old is slowing it down?
No, quite the opposite. As linseed oil sits in storage it finds enough oxygen to begin polymerization. The result is that it will cure faster. I thought about what you did . Is it possible that you waited too long to wipe and at the high temperature the oil cured enough that the excess was not all wiped off? If oil not penetrated is not wiped it could take many days for the surface oil to cure to where it will no longer transfer to your hands.
(06-05-2022, 07:10 AM)Bill Tindall Wrote: No, quite the opposite. As linseed oil sits in storage it finds enough oxygen to begin polymerization. The result is that it will cure faster. I thought about what you did . Is it possible that you waited too long to wipe and at the high temperature the oil cured enough that the excess was not all wiped off? If oil not penetrated is not wiped it could take many days for the surface oil to cure to where it will no longer transfer to your hands.
No, I don't think waiting the hour that I did was too long. We'll see. I'm going to try putting poly on later this week.
Two weeks AFTER posting this and it's still not wet wet, but not dry.
I had the leg assemblies sitting on top of the table top to mock up positioning. Left them there over night. When I came back, the assemblies had transferred a bit of oil where they touched.
How much trouble am I in here and is there a way to fix it?
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