Tung oil finish help needed

[Firewalker]

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

[Skew ChiDAMN!!]

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?

[woodcutta]

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

[Firewalker]

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.

[Skew ChiDAMN!!]

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. The drying time could probably be reduced for Danish, but I've no need to experiment. [shrug]

[Firewalker]

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

[Don Nethercott]

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

[Skew ChiDAMN!!]

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: