Wood Finishing: Tips (and possible pitfalls)

raghupb

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This thread maybe relevant for speaker box builders and possibly amp casing/enclosure builders

I dabble in woodworking projects from time to time. My interests are design, wood selection/procurement and finishing.
The actual carpentry a.k.a heavy lifting and skilled work is left to professionals. I simply don't have this skill, patience or accuracy.

The Elbow Grease Steps:
Sand, sand again, sand yet again. If you have a sanding machine your elbows, shoulders and back will be grateful
I use 80/100 --> 150 --> 220 grit sandpaper on raw wood. 3 steps should be more than enough for most woods or wood veneers. If you are anal do a 320 grit sanding after 220.

Sealing wood:
I have used nitrocellulose based sealants in the past. It gives a nice thin coat of protection to the wood. Apply 2 coats of NC sealant (sanding between coats). These days, I stay away from this due to the vapors (VoC) and dust. NC sealant does not stain or darken the wood. Ideal if you want to preserve the color of wood used.
Brush on or use cloth to apply NC sealant on raw wood. Use gloves if not using a brush. Adjust viscosity based of wood species. Very hard wood species can be brushed with sealant. Porous wood may require cloth application (in circular motion)
Caution: Use an N95 mask

My substitute for pore sealing and protection now is Boiled Linseed Oil (BLO). This is raw linseed oil with additives to speed up drying.
Warning: BLO contains some lead as an additive.
Flood the surface with BLO and rub the oil into the wood. After 15-30 mins, wipe of the excess oil. Vigorously rub down the wood in straight, along the grain motion.
Allow to dry for at least 24 hours. If there are any nibs, sand down with 320/400 grit paper. Apply 1-2 coats. After 2nd coat allow two days of drying time.
Note, that BLO will darken wood immediately and over time.
Caution: The cloth that is used to apply BLO should be dried out flat in the open for at least 8 hours before disposal. BLO soaked cloth/rags can result in spontaneous combustion when lumped and thrown in the waste bin.

Top coats:
If using NC sealant, use NC polish/varnish. Sheenlac is a good brand. Polyurathane (PU) finish requires a workshop and good ventilation/masks.
I have never done PU top coat due to lack of space and equipment. Have used simple polish/varnish with cloth application. This is a tricky part.
You need to thin down the varnish/polish with an NC thinner for easy application.
Long strokes with lint free cloth along the grain without any stops. Apply 1-2 coats. Buff with lint free cloth in between (or sand down with fine grit paper).
Caution: Use N95 masks if using NC/PU based products

Using Danish Oil: This is raw linseed oil with additives (no lead) to harden quickly, some resins, turpentine and PU varnish.
A kinda all-in-one material. This is to be used on raw wood surfaces or BLO treated surfaces, not after any chemical based sealants.
The method is very similar to using BLO. Flood the surface, rub it in, remove excess oil after 15-30 mins.
I usually allow for 24 hour drying, but wet-on-wet method may be used too. Apply, wait for an hour, rub down with cloth or fine grit sand paper, reapply. Repeat 2-3 times. Allow final coat to dry for 24-48 hours before a final rub down. You may use car wax for final rub down.
This does not give a mirror shine like chemical based polish or PU. Instead, it gives a low sheen.
Note: If you are sensitive to turpentine of varnish smell, use a mask.

In all my experiments, I have found that NC/PU based finishes give a shiny, super smooth look/touch.
Oil based finishes give a low sheen, kinda antique look. Smoothness is on how much you rub it in (elbow grease).
So, for anyone attempting wood veneer cabinets for speakers or wood enclosures for amps, give these a try.

My current furniture projects will culminate in 7-10 days. Will post pics then.
As a side project, building a couple of wood amp enclosures for myself and @Prodigy.
Will update on these too.

Cheers,
Raghu
 
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Ah ....
There had to be a pitfall :D
Danish Oil has worked for me well enough in the past, but this time it decided to act up.

I'm currently working on Acacia finger jointed boards for the first time. As per carpenter, it is fragile. Well ... I believe him.
It is a lovely board to sand (my territory). Did the usual 100-150-220 grit sanding on bare wood.
Applied 2 coats of BLO as described in thread starter (apply, set aside for 30 mins, remove excess oil, rub down, dry for 24 hours)
This step came out okay.

Then applied a coat of Danish Oil on it, the top coat (same procedure as BLO), but there is some tackiness or sticky surface.
This may be due to my mistake or the weather (it has been raining for the last couple of days).
Anyways, since I do open air drying, it has attracted dust and has become yuck.
Have to re-sand back it back using 150-220 and then try a mix of 2:1 Danish Oil with turpentine as thinner.
This time I'll keep it indoors in a ventilated place and hope that it works out okay.

So much for the joy of smooth finish :(

Cheers,
Raghu
 
Update:
I realized my mistake. Had applied Danish Oil and wiped it down lightly due to dry weather.
Was lazy to the vigorous rub in. Rains for a couple of days played spoilsport.
Anyways, putty blade to the rescue. Stripped the tacky layer down after "wetting" with turpentine.
The deep coloration is still there which is desirable, but I have to re-sand and re-apply the finish.

Cheers,
Raghu
 
@raghupb
Raghu, when I applied boiled linseed oil on wooden tonearm parts I had DIY-ed a few years back, it took many days to dry. Even after weeks it still felt tacky though it wasn't wet any more. After buffing the finish was matte. Eventually I sprayed acrylic clear coat from a can because I wanted the shiny finish.

Despite the long curing time I like the fact that BLO does not stain the wood. This is great if one desires natural looking wood grain.
 
@raghupb
Raghu, when I applied boiled linseed oil on wooden tonearm parts I had DIY-ed a few years back, it took many days to dry. Even after weeks it still felt tacky though it wasn't wet any more. After buffing the finish was matte. Eventually I sprayed acrylic clear coat from a can because I wanted the shiny finish.

Despite the long curing time I like the fact that BLO does not stain the wood. This is great if one desires natural looking wood grain.
In my experience, BLO and Danish Oil darken the wood while popping the "grain".
It may be due to additives added or some oil soluble stain used in the preparation of the final oil/mixture.
You are right, these oils highlight the wood grain better than any other chemical based sealant/finish and give it a nice warm glow.

Cheers,
Raghu
 
I used BLO for amplifier face plate. Same experience as @jls001 mentioned, wet for many days. May be a good buffing with multiple coat required for a factory finish.

Yes it makes the wood darker ( I would say the color same when your moist the wood), I needed even darker so saw a tip online to add coffee or tea water to add color to wood (dark brown or burgundy).

Another use of BLO I found was, after recent house shifting did easy touch up with this for the scratches in the furniture. A simple cosmetic makeover until a proper polishing is done. Happy with the outcome.
 
In the enthusiasm of working with wood, I sometimes get carried away.
In 2015, I designed a TV unit + showcase. It looked good on my computer screen.
When the unit got done and placed in the living room it was a monstrosity.

Another thing that happened towards the end of 2015 was I acquired my current speakers, KEF R300.
This set about a cycle of component changes and living room layout changes.
So, I tore down the "AV unit", reused and resized the shelves to make a smaller/sleeker AV rack.

The TV+showcase, AKA Behemoth
2015-TV-unit-org.JPG

Tear down to a smaller AV rack
rig-2-sm.jpg

The side units and the crown of the hutch portion went off to my parents place.
They really have use for storing "stuff". The hutch shutters, back sheet (behind TV) and one mid shelf was leftover.
This time around, I decided to use them up for a couple of small projects at my parents place.

Shutters for a hole in the wall. The frame to host the doors was another type of wood, Pau Rosa
The door panel frame itself is ply/veneer (Bubinga wood) from the erstwhile TV-unit.
2022-Shutter-hole-in-the-wall.jpg

Shutters for attic. This was from the back sheet of TV-unit. This was ply with one side veneer.
The other side uses some MDF/laminate extra sheet from the more recent chest of drawers project.
Same material used in the door shutters above (for hole in the wall shutters)
2022-Shutter-attic.jpg

The shutters from the hutch unit (square ones) are still lying around for some brainwave ;)
I'm happy that I could put the leftover wood to use.
The only cost I incurred now was labor for carpentry and hinges/hardware

Cheers,
Raghu
 
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A couple more small projects also done using leftover wood. Awaiting finishing though, which is my hobby.

Nested stools in Bubinga hardwood
nested-1.jpg nested-2.jpg

After sanding through 100-150-200 grit and first coat of Boiled Linseed Oil, the natural color and grain of wood looks quite good.
The legs have sanded down to a butter smooth finish. The top plank itself has some niggles due to softer grain sections (the darker stripes).
I may attempt to fill these with wet-on-wet sanding. If it works out, good. Otherwise no worries.
stool-blo-1.jpgstool-blo-2.jpg

Kitchen over the counter wall unit
Carcass/box made from ply and double side teak veneer. Had a few odd lengths from a previous project.
Shutters from an old bathroom door. Replaced the bathroom door few years ago as it was damaged at the bottom (water damage).
Was able to reclaim 4 planks and a few slats of teak wood, 45 year old wood :) This unit will have a crown from an old staircase handrail.
The mid shelf is Makore hardwood. These were the only pieces I could find in the stash. They have been damaged by borer insects in the tree itself, it seems. Anyways, lovely orange colored wood, sands down very well.
kit-wall-unit.jpgshutter-shelf.jpg

Will post a few more pics after they get polished and installed.
Thanks for looking.

Cheers,
Raghu
 
A beautiful, well-constructed speaker with class-leading soundstage, imaging and bass that is fast, deep, and precise.
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