Plywood edges dusty and “washed out” after sanding
ignorantenthusiast
| Posted in Finishing on
Hello. I am making a floating box-style wall shelf out of 3/4″ baltic birch plywood with exposed edges and have run into a sanding question. After sanding the first piece, I realized that the edge becomes noticeably dustier, lighter tone and looks kind of “washed out”. The problem seems to be that the end grain plies really absorb the dust. I vacuumed the edges and cleaned with a damp cloth which helped somewhat but not enough and it also made the surface rougher again. For me the appeal of plywood is the crisp contrast between the light and dark plies rather than a monolithic cloudy look so I’m curious how others deal with finishing exposed plywood edges. Any tips much appreciated.
Replies
Here is also an image of that condition - before sanding (top) and after (bottom).
Sand a scrap cutoff just like you did your parts, use compressed air to blow it clean or use the vac on it, then test your finish on the scrap. The contrast will probably come back when you apply a coating.
What mj said. You can also try sealing it before sanding.
Use mineral spirits or denatured alcohol if you wipe the edges.
The water is soaking in and raising the grain making the edges rough again.
Mike
I think a major part of the issue is that you are getting micro tear out of the end grain which will never effectively sand out.... If it were me I would either use a sharp 80 teeth plywood blade on the tablesaw or consider use a "compression" spiral router bit. Either one will give a cleaner edge to your cuts!
I applied two thinned down shellac coats the edge of my Baltic birch plywood, then sanded the edge to 220 grit to get detail you are seeking.
@jql - this is really interesting - so you shellacked, then sanded. Did you re-shallac after to get the shellacked look? Or was the entire point of the shellac just to bring out the definition again?
What JQL said +.
I’ve done this with drawer sides.
You must sand to higher grit (240/320). End grain, as half the plywood is, requires that to really shine and not get that dusty scratchy look. A few hand plane strokes will bring out the best contrast but baltic birch will wear down the blade very fast.
I've done this a number of times. You just have a lot more sanding to do working up through the grits until you achieve a polish on all of the layers. You can see considerable roughness in most of the layers. You need to start with a very coarse grit (probably 80) and sand until all of the layers have a similar smoothness and scratch pattern. Only then should you advance to the next grit and then do the same for all grits until you have a good polish on all layers.
This will a lot easier and more accurate if you have a stationary belt sander that you can change the belts on as you go.
And, to add a detail to that, be sure to blow out the sanding dust/broken off grit after using each grit before starting to sand with the next finer grit. Otherwise the broken off grit pieces will keep putting coarse scratches in the work.
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