cedarhorseworkshop Posted July 28, 2014 Report Share Posted July 28, 2014 I've searched the forums and can't seem to find anything on this topic. I read that shellac works well over the top of BLO, but I haven't read anything about polyurethane. The project I'm thinking of trying this on is very small. It's a wooden bottle opener. I apply the BLO on the lathe and am wondering if polyurethane will work over the top of the cured BLO. I'm looking for the added texture and look of the oil finish but I also want the protection of the poly. I've heard that it's a good idea to let it dry for about a week. Has anyone tried this before? Good results? Quote Link to comment Share on other sites More sharing options...
Guest Posted July 28, 2014 Report Share Posted July 28, 2014 Yes, assuming you are using an oil-based polyurethane they are perfectly compatible. This will work fine. Next time you could probably even mix 50/50 poly and BLO when you apply it on the lathe. You will get the look and protection you want all in one step. Quote Link to comment Share on other sites More sharing options...
Byrdie Posted July 29, 2014 Report Share Posted July 29, 2014 Not an expert on finishes so I'm sure I'll be corrected if I get this wrong but I believe if you're going to use a hard film finish over an oil you need to make sure the oil is thoroughly done drying or you're going to get hazing and spots under the film finish from the oil off-gassing and weeping. This can sometimes take weeks and I think I've heard of the rare instance in which it took longer. Quote Link to comment Share on other sites More sharing options...
Guest Posted July 29, 2014 Report Share Posted July 29, 2014 yes you do want to make sure the BLO is cured. OP said the BLO was cured so i took his word for it. Honestly I have put poly (and shellac) on top of BLO the next day and it was fine. That was before I "knew any better". But I also now know that poly on top of BLO does not look much different than poly on top of bare wood. So if I am using poly I skip the BLO. Quote Link to comment Share on other sites More sharing options...
cedarhorseworkshop Posted July 29, 2014 Author Report Share Posted July 29, 2014 Thanks for the information guys, I really appreciate it. Byrdie, was it possibly raw linseed oil? I've heard of the taking a very long time to cure, but never the boiled stuff. Mr. Woodsap, I'm going to give that 50/50 thing a try this week, that sounds pretty cool. If plain poly is going to have the same effect, it would have to be brush-on, wouldn't it? Would a spray can have the same penetration? Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted July 30, 2014 Report Share Posted July 30, 2014 Boiled linseed oil can take months to fully cure, especially if it is applied a bit to heavy in cold weather. Don't ask me how I know ... Quote Link to comment Share on other sites More sharing options...
Guest Posted July 30, 2014 Report Share Posted July 30, 2014 I guess I have always had a light hand with it. I apply just enough to get some color and wipe off the excess. Quote Link to comment Share on other sites More sharing options...
cedarhorseworkshop Posted August 1, 2014 Author Report Share Posted August 1, 2014 That's what I usually do too Mike, just some color and then wipe off the excess. Quote Link to comment Share on other sites More sharing options...
Byrdie Posted August 1, 2014 Report Share Posted August 1, 2014 To my knowledge oil finishes, in general, take longer to cure and ones that are absorbed take even longer. I'm not a finishing expert and I don't even play one on TV. But I do tend to leave my finishes cure a bit longer than the suggested time just as a matter of course. Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted August 1, 2014 Report Share Posted August 1, 2014 ... which is why I am so fond of shellac ... Quote Link to comment Share on other sites More sharing options...
Anna Baldo Posted September 25, 2019 Report Share Posted September 25, 2019 I am so happy to hear this. The mice eat the BLO like it is candy and the edge of the area rug where the BLO touched. I am disgusted! Quote Link to comment Share on other sites More sharing options...
Coop Posted September 26, 2019 Report Share Posted September 26, 2019 ?? Perhaps the BLO is not the problem here! Quote Link to comment Share on other sites More sharing options...
Rio Vista Andy Posted June 10, 2020 Report Share Posted June 10, 2020 I too have used BLO with an oil urathane top coat, both plain and poly. First attempt, wore out a scraper. You have to let each coat of BLO dry for 24-48 hrs and if thick 4-5 days. I normally use 3 coats of BLO followed by 2-3 coats of urathane or poly. As my projects lately have used poplar (Tulip) this gives a great color and grain highlights. Especially as I sum bleach the heartwood to near white color. Regards Andy Quote Link to comment Share on other sites More sharing options...
DrHillymyboy Posted July 12, 2020 Report Share Posted July 12, 2020 On 6/11/2020 at 1:52 AM, Rio Vista Andy said: I too have used BLO with an oil urathane top coat, both plain and poly. First attempt, wore out a scraper. You have to let each coat of BLO dry for 24-48 hrs and if thick 4-5 days. I normally use 3 coats of BLO followed by 2-3 coats of urathane or poly. As my projects lately have used poplar (Tulip) this gives a great color and grain highlights. Especially as I sum bleach the heartwood to near white color. Regards Andy The issue is how long after the BLO has been applied (to pine) can an oil-based stain/dye and polyurethane sealer be applied? It's exceedingly difficult to find related info. The answers I've seen claim that a sealer can be applied a few hours after the last layer of BLO has been rubbed off. Others say one must wait 30-45 days after the last layer of BLO has been rubbed off in order for the BLO to be cured. Which is it? Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted July 12, 2020 Report Share Posted July 12, 2020 IMO, although the oil based stains and finishes should adhere to the BLO when it is dry to the touch, it would be better to wait until the BLO fully cures (no longer smells) so that it isn'trying to off-gas under the top coats. But I question the advantage of using BLO in the first place. What benefit are you expecting from it? Quote Link to comment Share on other sites More sharing options...
Tpt life Posted July 12, 2020 Report Share Posted July 12, 2020 Isn’t BLO one that may or may not come with dryers in it? That would explain widely varying advice. Quote Link to comment Share on other sites More sharing options...
drzaius Posted July 12, 2020 Report Share Posted July 12, 2020 4 hours ago, Tpt life said: Isn’t BLO one that may or may not come with dryers in it? That would explain widely varying advice. BLO used to be literally boiled. That causes changes that allow the oil polymerize much faster (still slowly) that if it were raw (nearly forever). I don't know where you'd get that stuff now. But virtually all BLO available commercially contains dryers & I'm sure different formulations will behave a little differently Quote Link to comment Share on other sites More sharing options...
Mark J Posted July 12, 2020 Report Share Posted July 12, 2020 I believe the thickness of the application is also a factor. Quote Link to comment Share on other sites More sharing options...
DrHillymyboy Posted July 13, 2020 Report Share Posted July 13, 2020 16 hours ago, wtnhighlander said: IMO, although the oil based stains and finishes should adhere to the BLO when it is dry to the touch, it would be better to wait until the BLO fully cures (no longer smells) so that it isn'trying to off-gas under the top coats. But I question the advantage of using BLO in the first place. What benefit are you expecting from it? I'm a first-time novice at this, but my intention is to use the BLO to protect the sealed wood from drying out too much and crumbling. I'm assuming (perhaps wrongly?) that ultra-dry wood is as bad as rotted wood. Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted July 13, 2020 Report Share Posted July 13, 2020 BLO does not "re-hydrate" dry wood, it only forms a mildly protective barrier against the penetration of dirt and water. It also adds a warm amber color that looks good on some species, and horrible on others. If the wood you are using is punky, so dry and rotted that it feels like a sponge, then infused resin stabilization is about the only way to make it suitable for building. Since this requires a vacuum chamber and an oven, stabilizing larger pieces isn't practical. If the wood you are using is hard enough to shape into joints and hold a screw, its fine. Attempting to saturate the wood with BLO will only result in a piece that 'weeps' oil for weeks or months. Voice of experience.... Quote Link to comment Share on other sites More sharing options...
Mark J Posted July 13, 2020 Report Share Posted July 13, 2020 What wtnhighlander said. There is no surface coating that will prevent water from migrating back and forth between wood and air. Many will slow that process down, and some more than others, but nothing stops that process. Wood will eventually reach equilibrium moisture content, but even in the desert that isn't zero. And wood does not crumble because it is dry-- the fibrous structure of wood is not dependent on water molecules. So if you are encoutering crumbling there is another process, such as rot, at play. But wood can and will crack if taken from wet to EMC too quickly. Hope that helps. 1 Quote Link to comment Share on other sites More sharing options...
drzaius Posted July 13, 2020 Report Share Posted July 13, 2020 6 hours ago, DrHillymyboy said: I'm a first-time novice at this, but my intention is to use the BLO to protect the sealed wood from drying out too much and crumbling. I'm assuming (perhaps wrongly?) that ultra-dry wood is as bad as rotted wood. Wood will dry out to the point where its moisture content reaches equilibrium with the humidity of its environment. Even if in a desert with 0% humidity the wood will not degrade as it looses moisture. What may happen is cracking or warping. Nothing can be put on it to prevent that from happening. Another popular misconception is that wood needs to be "nourished". It does not. Wood is already dead & needs no nourishment or moisturizing. 1 Quote Link to comment Share on other sites More sharing options...
JP Cordon Posted September 11, 2022 Report Share Posted September 11, 2022 Polyurethane over BLO is a great finish, I use it on most of my projects with results exceeding clients expectations, however it’s a process and a challenge to anyone’s patience. I want to add to all answers above, which are accurate, that you have to check that the relative humidity is below 50% from the day of BLO application till the first poly application. Ideally between 30%-40%, based on my experience. 1 Quote Link to comment Share on other sites More sharing options...
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