Rosewood pores filled with dust

[Martijn]

Hi everyone,

I am building my first acoustic guitar, it is a Dreadnought kit from Stewmac.
As the rosewood back isn't very smooth, I would like to sand the inside of the guitar with 80 grit sandpaper.
But the pores of the rosewood get filled with dust, which gives the wood some kind of grey shade. Is there any way to avoid this?
Vacuuming or cleaning with a damp cloth doesn't seem to help.

Martijn

[gsr]

You could try blowing it out with compressed air.

[gitnoob]

Rosewood does have large pores. Maybe you're using cheap sandpaper and the abrasive is getting lodged in the pores? Never seen that myself, and a vacuum usually works for me, but perhaps turn the plate over and tap on it first to unlodge anything lodged in the pores.

[arie]

80 grit is really coarse and is probably rougher then the kit pieces came sanded at. work it down in grades to 220 or so. blow off with compressed air between grades at an angle to the wood or you'll drive the funk in deeper. Imo 220 is good enough for the inside of a guitar if you're sanding alone, but i'll usually finish off with a scraper after 220.

[redir]

A damp rag should work and it will raise the grain so you sand it down finer. I always go to 220 grit on the inside from 100 - 150 - 220. As was mentioned 80 is pretty coarse. After the 220 sand you can clean it with naphtha. When you French Polish you use pumice to fill the pores and that essentially is filling the pores with saw dust and sticking it in there with shellac.

[Martijn]

Thanks for the suggestions everyone!
I am going to try a different brand of sandpaper, and sand it up to 220.
For me 80 grit would be smooth enough on the inside of the guitar, but I'm curious if a finer grit will help to avoid the grey shade.

[arie]

what kind of paper are you using btw?

[Pat Foster]

Be careful with water; use very little. Dampening the wood, particularly if it's only on one side, could cause warpage. It could also discolor the wood, leaving lighter colored areas. But if you keep the water to a minimum, should be no problem with warpage or discoloration. I suspect bits of abrasive, as gitnoob suggested, might be the culprit, especially if it's cheap hardware store paper, like garnet.

I seem to have the best luck cleaning pores with a powerful vacuum, just using the hose, held almost directly onto the surface, so that there's lots of noise, like a shriek, indicating high velocity. Hope this helps.

Pat

[Ned Milburn]

As Arie stated, 80 grit is very coarse. Differences in hardness/density of regions of wood are such that sandpaper can often yield a non-level surface, hence the need of a hard sanding block if you go that route. Even with hard sanding blocks, for example, it is possible to create non-level surfaces on rosewood. I discovered this when shaping classical guitar rosewood bridges.

My technique & tool of choice is to finish my instruments (top/back/sides) with a hand scraper. This creates a smooth finish that is smoother than sandpaper can yield (unless you go to 1000 grit or above), and it allows me to ensure a contiguous flat surface. Any flat edged metal object can be made into a scraper, but commercial scrapers are available for very economical prices. Following with Redir's point, you can even do a light spritz with water and scrape the fluff with a scraper to flatten and clean a surface.

[dekutree64]

I also scrape rather than sand. But if I do ever need to clear dust out of pores, an old worn out toothbrush does a pretty good job of it.

[redir]

+1 on the scraper. It's the best way to prep surfaces in my opinion and in fact once good with one you can use it instead of sand paper for almost all applications. They don't work so well on spruce unless you are a grand master at sharpening one but for everything else they are the best IMO. And since they actually cut and produce shavings you won't fill your pores.

[arie]

jmo,

-air or vacuum to remove dust. it just plain works. no need to get exotic.

-sandpaper to 220 then scrape. and honestly i have a hard time believing the sm kit would need so much sanding other then med to fine finish prep.

-use no water. the back and side material is thin. risk of warpage is very high as well as possible color bleed off.

-use the basics: aluminum oxide, zirconia, or garnet sandpaper -no silicon carbide sandpaper.

.02 cents

[Martijn]

Thanks for the information, I appreciate everyones effort!
The sandpaper wasn't very cheap, but the abbrasive is grey so that probably caused the problem. Today I bought brown 3M paper.
I tried the tootbrush and a scraper to clean the wood, this seems to work. The vacuum wasn't powerful enough I gues as it didn't remove all of the dust.
Tomorrow I will let you know the result!