Tung oil finish help needed

I have been applying tung oil to my last project off and on for the last 2 weeks. I am using tung oil and I was originally impressed at how nice it looked and how easy it was. (no lap marks no sticking brush no "wet edge")

I wanted to put several coats on the top to create some water resistance.

The problem is that the tung oil finish is rough as a cob. The timber was sanded to 400 grit. First coat was thinned with mineral spirits. Actually the first 2 coats were thinned due to the viscosity of the tung oil. To be honest I don't remember if I sanded in between coats except between #1 and 2.

Anyway, I have the depth and sheen I wanted but it is rough to the touch. I took the steel wool to it but after getting the rough surface off I wonder if I am almost down to the wood again. You can see some blistering if you look at the right angle using a light.

At a glance you would never see it but I am too picky to let this ride. After using the steel wool it now has more of a mat finish to it. I hate to mess with this as much as I have only to shoot a coat of poly over it for protection.

What would cause the roughness after the finish? Is this normal?

Any help / advice is appreciated.

Scott

I generally apply Tung Oil in the way you describe, although I apply the first coats unthinned, using wet'n'dry instead of a brush to minimise raised fibres. This also depends on the type of timber you're using, of course. Your sanding between coats 1 & 2 should have the same basic effect though, so I doubt this is the problem.

Because it's thinned, the second coat may've penetrated the first and raised more fibres, but I imagine you would've noticed this when applying the third and done a bit more sanding, so it's a bit of a puzzle. Assuming the first coats sealed the surface and were fully dried before applying more, the only thing I can think of is air-borne dust settling out. Would this be very likely?

Firewalker,


When you say 'Tung Oil', which Tung oil are you meaning. Pure Tung oil or someting like Minwax Tung oil which is a mixure of Tung oil and Poly?

Woodcutta

Skew, the dust is a possibility although this would have been a grip of dust to cause this problem. I also wiped the tung oil on with a rag.......gave it 15 minutes to sit and off again with another clean rag as label recommends.


Woodcutta, the product is labeled as 100% Tung oil. I have seen quite a debate on if it is pure but this one seems to be. It is Rockler's brand.

Thanks for the help guys.

Ah. Then it might be the fibre ends lifting as they absorb the oil. A close inspection might tell... if it's "grittier" in areas where there's more end-grain (ie. the grain's not perfectly parallel to the surface) that's a good indicator.

I apply the first few coats with a rag and wet'n'dry while still wet, with 24 hours between coats. FWIW, I usually use around 400 grit for the first coat and work thru finer grits for each subsequent one. The slurry also acts as a grain filler. Normally only two coats need to be applied this way, but it depends on the timber. As a rule of thumb most hardwoods are fine but softwoods tend to need more.

Once I'm satisfied the surface is sealed & smooth then I'll wipe on, wait about 20 mins and wipe off... still leaving 24 hours between applications though.

I also use this method for so-called Danish Oil, mainly 'cos for me it works. :D The drying time could probably be reduced for Danish, but I've no need to experiment. [shrug]

Skew, thanks for the reply. This may be the case with the grain raising. It does seem grittier in those areas. I may hit the whole top with some 400 until I get it smooth again then build it up once again. I thought the tung oil finish would be an easy one but not so sure now.

One thing that is interesting is the viscosity of this tung oil. It is a bit thinner than honey and is hard to spread unless you use a hell of a lot. Is this normal? This is the original reason I thinned the second coat. Thanks again for your interest.

Will let you know how it goes.

Scott

I was taught to use a Tung Oil mixture with drying agents for the first coat, then pure Tung Oil for subsequent coats. I use Feast and Watson Floorseal (on bandsaw baxes, and is is smoother than a baby's b---.) Also using it on a Silky Oak table I am restoring - and looks and feels great.

I dry sand with 120, 220 and 320 then apply the oil with 400 (really soak the item with the oil), then 600, 800 and 1200 wet and dry, dipping the w&d into the oil to apply.

Make sure you wipe all excess off after each coat - use kitchen style paper towel as it is absorbent and soft.
Best of luck

Don

Scott, I can't say that I've used tung oil quite as viscous as you're describing, the thickest I've used would be comparable to dishwashing liquid concentrate. Quite easy to spread and I think it is a simple finish, especially compared to some!

I wonder if Tung Oil comes in various grades, sorta like Olive Oil? :confused: