Solvents

[Isaac Litster]

I have a few questions that are similar. I have a hemlock knot that won’t sand, and is relatively soft. I have heard of using solvents on oily woods some rosewoods, but I thought that was to finish it, and I can’t even use 120p for a couple swipes let alone power sanding or finishing. I tried using a buffing wheel with Tripoli, to smooth out a little, kind of worked. Now I have the wax from the trip. And the sap, gum, resins in the wood. How would you finish it? I need to sand and finish it, hopefully buffed danish oil. I need a solvent if some sorts, my experience trying to use paint thinner were bad, but what else could I use?

 

[Steve Tiedman]

Try a card scraper. They can be made at home from thin steel like handsaw steel (which is typically an alloy like spring steel, alloy commonly used to make... springs). Or you can buy them from any woodworking supplier for a few bucks. I really like this one. At the bottom of the listing is a video of how to sharpen and burnish any card scraper. https://lostartpress.com/products/crucible-card-scraper

Use the card scraper to get a very clean surface on your knot, then go back to the usual sanding of the piece overall. Knots can be rock hard compared to their surrounding wood, especially in softwood species. The surrounding wood will sand away faster than the knot, making the knot stand a bit proud of the surrounding surface. Use the scraper to pull-cut very fine shavings off the knot surface only (working from different directions) and you may get an acceptable surface in the end.

As for your finish coats, you may need to be prepared to accept a somewhat different look of your finish on the knot vs. the surrounding wood. Blame that on absorption into the different grain structure at different rates. A thick, multi-coat surface finish may blend it in, but typical Danish oil finishes may leave it looking different. Not bad by any means, just different. Use this piece as a learning experience and let Nature be your partner in it. Good luck!

 

[john lucas]

Seal the knots with shellac. Then sanding and finishing will go much easier.

 

[Michael Lombard]

Shellac should work, lacquer sanding sealer should work as well. What I use for soft spots - mostly punky spots, but there is no reason it will not work on knots as well, is a product called
PC-Petrifier. (yes, that's the way it is spelled, and with the dash). Available from, of course, Amazon. It is fairly inexpensive. It goes on milky white but dries clear in a couple of hours. I often re-treat the same spot if it is still a problem area. I have never had a problem with any finish - either a surface or a penetrating finish.

 

[Richard Coers]

If it still needs to be sanded, mineral spirits and black silicon carbide sandpaper to wet sand it. If the wood has not been heated to set the sap, it could weep for years.

 

[Isaac Litster]

If it still needs to be sanded, mineral spirits and black silicon carbide sandpaper to wet sand it. If the wood has not been heated to set the sap, it could weep for years.

Wet sand with mineral spirits?

 

[Isaac Litster]

Try a card scraper. They can be made at home from thin steel like handsaw steel (which is typically an alloy like spring steel, alloy commonly used to make... springs). Or you can buy them from any woodworking supplier for a few bucks. I really like this one. At the bottom of the listing is a video of how to sharpen and burnish any card scraper. https://lostartpress.com/products/crucible-card-scraper

Use the card scraper to get a very clean surface on your knot, then go back to the usual sanding of the piece overall. Knots can be rock hard compared to their surrounding wood, especially in softwood species. The surrounding wood will sand away faster than the knot, making the knot stand a bit proud of the surrounding surface. Use the scraper to pull-cut very fine shavings off the knot surface only (working from different directions) and you may get an acceptable surface in the end.

As for your finish coats, you may need to be prepared to accept a somewhat different look of your finish on the knot vs. the surrounding wood. Blame that on absorption into the different grain structure at different rates. A thick, multi-coat surface finish may blend it in, but typical Danish oil finishes may leave it looking different. Not bad by any means, just different. Use this piece as a learning experience and let Nature be your partner in it. Good luck!

Sorry, what I meant by knot is a 9” bowl/platter from a beach log that was old growth hemlock, so it’s not necessarily a knot, but it isn’t a Burl, the grain is twisted and figured, but there isn’t a branch, the wood smells strongly, and the entire thing needs sanding, but the resins prevent it.

 

[Isaac Litster]

Seal the knots with shellac. Then sanding and finishing will go much easier.

Sorry I didn’t say really what it is, it is a bowl/platter made of old growth hemlock that has been on a beach after floating in the ocean, it is not that it has knots, it is one. It is ~9” diameter and has twisted grain. It is dense, but it is so resinous that it cannot be sanded how it is.

 

[Richard Coers]

Wet sand with mineral spirits?

I assumed you were having an issue with the resin content of the knot ( like others who believed you when you said knot) and that is how I address sanding high resin wood.

 

[Steve Tiedman]

When is a knot not a knot...?

Okay, well, I have no other experience to offer, sorry. I'm 150 miles from Lake Superior, but about 10x further to an ocean. I hope you find the right combination to make that lump of lignum work for you.

 

[Steve Tiedman]

Can you post some photos of this knot?

With your description of the beach-found wood that had possible long-term contact with seawater, is it possible that what is causing the issues is the result of that environment? Has the wood taken on some excessive mineral content (salt)? Is the wood already degrading?

My questions only lead to speculation in my mind- I truly don't know the answer, but if this is some old piece of wood that has spent time in a harsh environment, part of me wonders if this wood may not be salvageable as you've planned.

Maybe take a completely different, opposite approach. Rather than make it smooth, make it rough. Instead of sanding smooth on the lathe, put a wire wheel on a drill and then scrub a texture into the surface while it spins on the lathe. It will remove any tripoli wax. Then thin your danish oil just a little bit and let it really soak in to the textured surface. Crazy ideas, but this sounds like an unconventional piece of wood.

 

[hockenbery]

Hemlock sandblasts with nice results.
The hard and soft parts will give raised grain lines from the hard part.
In log growth these are fine lines.

Bill Luce did a lot of skeleton pieces from hemlock by blasting all the soft parts out leaving the hard grain as rib sections.

Wire brush might yield a similar type surface but it could be too aggressive for hemlock

 

[Isaac Litster]

I assumed you were having an issue with the resin content of the knot ( like others who believed you when you said knot) and that is how I address sanding high resin wood.

I think I will try that, or just sand and use lots of cheap disks.

 

[Isaac Litster]

Hemlock sandblasts with nice results.
The hard and soft parts will give raised grain lines from the hard part.
In log growth these are fine lines.

Bill Luce did a lot of skeleton pieces from hemlock by blasting all the soft parts out leaving the hard grain as rib sections.

Wire brush might yield a similar type surface but it could be too aggressive for hemlock

Probably not on this piece, it is pretty much finished aside from some spot sanding.

 

[Isaac Litster]

Can you post some photos of this knot?

With your description of the beach-found wood that had possible long-term contact with seawater, is it possible that what is causing the issues is the result of that environment? Has the wood taken on some excessive mineral content (salt)? Is the wood already degrading?

My questions only lead to speculation in my mind- I truly don't know the answer, but if this is some old piece of wood that has spent time in a harsh environment, part of me wonders if this wood may not be salvageable as you've planned.

Maybe take a completely different, opposite approach. Rather than make it smooth, make it rough. Instead of sanding smooth on the lathe, put a wire wheel on a drill and then scrub a texture into the surface while it spins on the lathe. It will remove any tripoli wax. Then thin your danish oil just a little bit and let it really soak in to the textured surface. Crazy ideas, but this sounds like an unconventional piece of wood.

It is unconventional, I imagine that it is similar to what is considered fatwood in that the tree was dead, and so the resins soaked into the surface, especially this swirl dense not which prevent it from rotting while the rest of the tree rotted this slice that was on the surface, came off as part of a layer so it was live edge on one side and rotten on the other you can see that in the second photo anyway possibly the resins prevented the rot in some parts of it and are also preventing sanding.