Sticky Finish - any ideas?

[Rhythm House Drums]

So I've used wipe on poly on top of danish oil with walnut tons of times and have always had good results. So I'm really baffled as to what has gone wrong, and hope maybe some of you can put in your ideas.

I used Watco Danish oil on walnut that was sanded to 220. Used two very light coats and rubbed it down after. It felt nice and dry - I gave it 3 + days to dry more before I put the minwax wipe on poly. I mixed about 50/50 the satin with the gloss, and shook up both containers before I mixed. Mixed in a plastic cup, and stirred for a few. ..proceeded to rub it on and all went well. I was going to do a second coat later that night, but time got away from me. I went out about 6 hours after the first coat to find it still tacky. It has been humid, but my shop is temp controlled. I waited till morning and still tacky. Now a day later and I've put this piece on the lathe and taken a cloth to it to try and buff out the tackiness... Seemed to help some. Brought the drum inside where it's been for a good 5 hours now and still feels like it's oily/dirty. Not really tacky, but not the way it should feel.

Another piece of info is that I inset a section of a different wood after I put danish oil on the main section. so no danish oil on this inset maple. it's sticky as well. Both cans of the poly are less then 3 months old and been stored in temp controlled shop.

Should I not have shaken it up? I seem to remember mixing them before... is this a no-no? I used what I had left of the mixture and wiped on a bit to some scraps of different woods in the shop. I'll know in the AM if it's the mixture. But I would think it's OK to mix? I just wanted something with a bit more gloss than satin, but not as glossy as the gloss

Suggestions and / or advice is welcomed!

 

[ehpoole]

You mention your shop is temperature controlled, but what is your *actual* humidity level in your shop? I ask because a cool shop is not necessarily a dry shop, so it is always important to be aware of your shop's actual humidity level when finishing.

In cool and/or humid conditions polyurethane requires more time to cure. It also sounds like your wipe-on coat was probably much too thick in which case that will increase the drying time as well. It is also possible that the Danish Oil, which is not a film-forming finish, may have been applied to thickly as well leaving behind an undesirable surface film. A wipe-on coat of most any finish should be an extremely thin coat (unlike a typical brush-on coat) that requires *many* repeated coats to build up your final film thickness.

As for mixing, you should always mix your polyurethane before use -- especially so if it has flatting agent (i.e. is not high gloss) added.

I'm sure even better advice is soon to follow as I am not an expert on finishing.

HTH

 

[Larry Rose]

The poly could be could be too old. I had that problem with some brush on Minwax Poly and it's the only thing I could think of that caused it.

 

[Joe Scharle]

I've experienced this twice. The first time I just waited until it finally dried enough to sand off. But the second time, I did some sleuthing and found high moisture in the workpiece. I did have a clue, because the finish had a slightly cloudy cast.

 

[Jeff]

The poly could be could be too old. I had that problem with some brush on Minwax Poly and it's the only thing I could think of that caused it.

+1 perhaps. Only 3 months old in your hands, but how long since being manufactured and kept in a sealed container? The Minwax site doesn't have any information about manufacturing dates/expiration, etc. They do have a "contact us" link that you could try. Maybe you just got a bad batch and they may offer to replace it.

 

[CarvedTones]

YIt is also possible that the Danish Oil, which is not a film-forming finish, may have been applied to thickly as well leaving behind an undesirable surface film.

Watco Danish Oil is described in their literature as a varnish and has some "proprietary resin" listed in the MSDS. It's also important to note that while no actual Danes are harmed in the manufacture of the "oil", some could be harmed by breathing the vapors (it's about half spirits) in the application. Anyway, I think it is supposed to be film forming; whether it is or not is another matter. But since he has had good results with poly over it in the past and the maple insert with no "oil" on it also is sticky, I think the poly is the issue.

 

[bluedawg76]

Watco Danish Oil is described in their literature as a varnish and has some "proprietary resin" listed in the MSDS. It's also important to note that while no actual Danes are harmed in the manufacture of the "oil", some could be harmed by breathing the vapors (it's about half spirits) in the application. Anyway, I think it is supposed to be film forming;

Danish oil is an oil/varnish mix so it's not intended to be a film like varnish but rather give that "in the wood" look. I think the watco version contains linseed oil, not blo, so it takes considerably longer to cure than blo.

did you check the MC as Joe suggested? If they're "dry", I'd guess that one or both of the 2 poly's was bad. Were you making a semi-gloss (satin + gloss)? Definitely mix them well -don't believe that nonsense about introducing air bubbles in the finish.

I've had a similar finishing woes before i.e. remained tacky for about a week and never really cured hard, but remained soft. It was definitely the finish, which was from a recently purchased unopened can . The best part was that I applied this stuff to every part of 2 adirondack chairs (~11 seat slats each, 7 back slats, legs, arms, etc.) and waited for about a week for the finish to be "dry" enough so that I could scrape it off and start over :BangHead:.

Sam

 

[Bill Clemmons]

Kevin, I've experienced the same thing on two projects this summer. I use a BLO/Varnish/Thinner blend as my standard finish, and usually it dries within 24 hours. But this summer it's taking much longer. Like you, my shop is temperature controlled, but as Ethan pointed out, that doesn't necessarily mean the humidity is low.

On the second project, it's still in my finish room and I've got a fan blowing across it. That has helped dry it out. Good luck.

Bill

PS: I've talked to a couple other woodworkers and they are having the same issue this summer, so we're not alone.

 

[wndopdlr]

You mention your shop is temperature controlled, but what is your *actual* humidity level in your shop? I ask because a cool shop is not necessarily a dry shop, so it is always important to be aware of your shop's actual humidity level when finishing.HTH

Very interesting, and a mistaken assumption( and we all know the meaning of THAT word)that I have been making. The question, then, is, what is a good RH for finishing or woodworking in general?

 

[Howard Acheson]

Couple of points. First, your Watco may be old and not drying/curing properly. If you apply an oil based clear coat on top of an undercoat that is not dry, both the undercoat and the top coat can have slow drying or no drying.

Second, There is no need to shake or stir a clear, gloss finish. There are no flatters in gloss finishes so there is nothing to stir back into suspension. Non-gloss finishes however should be thoroughly stirred--not shaken--to get the flatters back into suspension and evenly distributed into the finish. 100 strokes in one direction followed by 100 strokes in the other keeping your stirrer in contact with the bottom of the can will give you the proper results. Once stirred, you can mix the gloss and satin together.

Finally, as already said, high temperature and humidity can have strange affects on finishes.

Oh, one final point for the future. If you intend to have you final coat be a clear varnish or poly varnish, it's a waste of money to start with Watco. Watco is nothing more than varnish, linseed oil and lots of thinner. Watco is intended to be a complete finish. If all you want is the figure and grain "popping", just wipe on a light coat of boiled linseed oil, let it set for 15-20 minutes and then wipe it dry. Let it dry 48 hours and apply your clear coat.

 

[Rhythm House Drums]

Thanks for your suggestions and comments. I found a setting on my unit that says "dry" so I"m guessing its a bit of a dehumidifier. We'll see. Anyhow, I ended up sanding the drum back down, and did a 50/50 BLO/Mineral Spirits mix rubbed in and let sit for 10 min or so before I rubbed it off. I"ll give it a few days and then try out the wipe on poly topcoat if my tests come back ok...

I took a scrap of walnut and put a coat of the satin, gloss and the mix side by side, I'll see how does in the AM.

Thanks for the tip on the BLO instead of danish oil. I acutally used to do this, I'd either do danish oil, or the BLO under poly. I had stopped using poly for a while so I was using lots of danish oil. So when I started using poly again.. I just kept using danish oil as my first coat. hopefully by thinning down the BLO, it'll dry in a day or two.

 

[ehpoole]

Very interesting, and a mistaken assumption( and we all know the meaning of THAT word)that I have been making. The question, then, is, what is a good RH for finishing or woodworking in general?

My recommendation is something between 40-60%, which also coincides with most people's comfort zone and reduces the risks of mold/mildew formation as well as rusting and corrosion of shop tools and equipment. You can, of course, get away with a broader range than that, but this is my preferred range.

My shop is only temperature controlled while I am in the shop or have a finish curing. The AC would never adequately pull down the humidity so I could (and did) easily have a 68F air-conditioned shop that was still at 85% humidity. The humidity would dip significantly over the course of the first few hours as it brought the room temperature down, but once the AC had caught up and began cycling on/off the humidity would then continue to rise. By the time the shop was cooled down and I was ready to get to work, the shop would be cold and clammy -- not my ideal work environment! -- and I'd find myself sweating in no time! This was not good for me, my tools and wood, or my finishing!

My health issues and medications make me very prone to overheating and sweating so this was an even bigger issue for me than just finishing -- or any of the other various concerns with respect to humidity.

So, I added a dehumidifier which I do run 24x7x365 (it is a low-temp model so it can run in winter) and which I have set to maintain a target humidity of 45-50%RH. Not only does this make for a much more comfortable shop (at most any temperature) but also greatly reduces (nearly eliminates) rusting and corrosion while also reducing unwanted wood movement during preparation and assembly, but it also works well for finishing.

Cost wise, the dehumidifier costs me, roughly, a maximum of about $12-15/month during the most humid months and next to nothing during the drier months. The larger dehumidifiers (50-70 pint units) are much more efficient than the smaller units and are the way to go. I have a 50-pint unit for my 2-car garage (about 525sq.ft. with 10.5ft ceilings) that drains into an external pump-reservoir unit that pumps the condensate up and out the same window as my window-mounted AC/heat (12,000 BTU) unit so that I don't have to bother with emptying the dehumidifier's collection bin.

HTH