Edward6311 - 9-17-2018 at 08:54 AM
Is there a type of oil or sealer someone would recommend to protect an unfinished soundboard? Or should I leave it as is? I would like to protect the
wood if I can from any possible staining but also not affect the sound quality.
Thanks for any advice
Omar Al-Mufti - 9-25-2018 at 03:29 AM
I tried brushing liquid egg white on the surface, leave it to dry then finish it with steel wool. It closes the pores.
In other cases I French-polished the whole sound board.
Lately, I prefer to leave it as it is. Every now and then I would clean any stains using rag and alcohol ( more that 90% concentration)
Time is on your side. As the wood oxidise, it turns darker and the stains will be less visible if any; It will be also harder to see any new stains if
they occur.
SamirCanada - 9-25-2018 at 10:09 AM
actually what Omar said above is great advice. but most importantly avoid any oil that will penetrate the soundboard
Omar Al-Mufti - 9-26-2018 at 12:57 AM
talking to European luthiers here in Vienna, they showed me some historical evidences that old lutes were finished sometimes with wax or hard oils.
They use those method regularly.
As Samir said, once oil penetrates into the pores, it's almost impossible to dry it out. The impact on sound would also be negative. However, wax is
harder to penetrate inside. Applying wax and rubbing it for long time repeatedly with clean towels would remove any extra wax, keeping only the pores
blocked and giving a semi-glossy finish.
Honestly I am too cowered to try any of the methods above, albeit the insurances I got from those luthiers.
majnuunNavid - 9-26-2018 at 02:31 AM
Omar, did applying french polish or egg white change the sound? I imagine the sound might improve with any pores filled...?
Omar Al-Mufti - 9-26-2018 at 03:06 AM
Hi Navid,
Honestly, the egg white didn't cause any noticeable change. I also didn't like the idea. It is too messy. It protects only against solid dirt, not
against liquid stuff. So in terms of protection, I wouldn't highly recommend.
As for the French polish, you will hear various opinions.
the French polish needs months to solidify to 100%. Once it happens, it makes the sound nicer, taking in consideration that the polish thickness is
not high.
there might be a very slight influence on volume though. In few cases the volume decreased slightly, but really not a big problem.
SamirCanada - 9-26-2018 at 07:49 AM
So the thing with French polish is that it's a bit hard to do a nice job. the first coat should be a sealer coat brushed on without oil, followed by
light sanding at 400 or 600 grit, then you can start to build the body with a light oil like lemon oil or mineral oil. It's also hard to do around the
bridge and other areas because of the pad used to apply it. that's why classical guitars tape the area under the bridge and do the polish before
gluing the bridge. the tape is removed with a sharp blade before gluing the bridge.
Regarding sound change... I think it's hocus pocus. No one could really tell the difference I am pretty sure. if they can, their ear is more refined
than 99% of the population. You will get a greater sound change by swapping to a new set of strings. just my opinion. I find the darkened look of old
ouds without polished tops is desirable and you will not get to that look if you seal the soundboard.
Omar Al-Mufti - 9-26-2018 at 08:10 AM
Samir...
I have never applied even first coats with brush....alwas used pad..even as sealer....it takes longer time but you end up with the thinnest polish
layer possible.
SamirCanada - 9-26-2018 at 10:49 AM
Maybe try it next time. 
with just the pad and no oil it makes it very sticky and
you are actually removing shellac when you feel this stickyness not applying it. Like you said though in the end it works both ways.