Ridges on lamination lines with tung oil burnished finish

All,

A newly laminated kitchen benchtop. Recycled dry hardwood, dressed square and true, then glued with crosslinked selleys pva glue and left to dry >1 week before burnishing with pure tung oil blended with 1/3 d-limonene ( citrus oil). The finish was sanded with a ROS to 600 grit before oil flooding, then wet sanding slurry to 1500 grit. On drying the finish is dull and looks starved in part.. also there are little teeny ridges ( feelable but too small to photograph) on each glue line and where small cracks in the grain are. The ridges seemed to form as the oil dried over say 5 days. After oiling and burnishing the bench was smooth and silky and looked great.

I use this finsh to finish my kayak paddles with great success all the time.

Any idea on what went wrong and how to fix this? Any idea what the ridges growing from lamination lines are? (Does tung oil swell as it dries? As the ridges are also on the fine cracks in open grain I guess its not a reaction to the glue).

I'm thinking sand with say 1000 grit and re apply oil?

Tom

Hi Tom,
The only reason I can think of is that you have used too much oil and it is now seeping back up through the wood. There's a couple of things that should work.

1. Use some paper towel or serviettes on the bottom of your ROS and run this over the bench. This will soak up the extra oil. You may need to do it several times. You can then resand at 1000 and then 1500. The finish should be smooth and polished then.

2. My own preference is to go back down through the grits to 600 and redo the process, but only add oil with a soaked rag rather than flooding.Then work back up to 1500 again.

Veneer doesn't seem to work as well using the flooding technique, probably because its not solid timber and absorption occurs at a different rate. The laminate is probably oversaturated as a result of only being a couple of mm deep.
If the veneer will take it, try using a 2000 and 4000 pad as well.

Hope this helps,

Regards,

Rob

Rob,

Its actually now dry and no longer oily and the ridges are hard - scratch off with a fingernail hard.

Also the laminate is lots of boards side by side, and the ridges are on the glue lines. There is no veneer.

I've tried sanding them off with 800 grit and re oiling ( working back up through the papers with oil) and the litttle things came back... it seems like the oil is expanding in a micro crack and growing up to form a ridge as it dries.

Any other ideas?

Tom

http://img.tapatalk.com/d/14/08/25/yqe8ytav.jpg

Here's a picture.

Have heard of pva also rising into ridges. Perhaps just rub with a nylon scorer instead of adding more oil. Not sure about hard burningshing oil, but rustins danish oil now has that as the last instruction.

Hi Tom,

Sorry I misunderstood.

Perhaps the oil is reacting with the glue? What glue do you use?

During the two years I spent perfecting my hard burnishing method I can only remember seeing the finish go flat and "ridgy" after excessive oil use. It could take a week or even two to show up, by which stage I was totally perplexed about the cause. I can only suggest that you take the wood right back to say 400 grit and begin the process again, but with much less oil. You can get a brilliant finish adding the oil to the wood with a saturated cloth, then letting it sit for 15-20 minutes and continuing up through the grits from there.

Why you are seeing the problem as worse at the glue lines is hard to say, but I think that with enough oil, the wood will expand and thus at the glue lines, you see some rising. That's my best guess.

If I can think of anything else, I'll let you know. It's too good a method and too reproducible to have to stop using it.

This is a table top I've just finished using Hard Burnishing Oil on, but I use this and Tung oil/white spirit mix (1:3) interchangeably.

For what it's worth, you might like to look at this thread. Maybe it will help.

Regards,

Rob

Thanks Rob. I think that is the only logical cause. I'll take it back and go again, this time with less oil. Might buy some HBO and use that in case it's my blend causing the hassles.