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Sanding scratches, a little tear out, and coloring Alder
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10123&t=52498		 Page 1 of 1
Author:  Conor_Searl [ Wed Oct 02, 2019 3:58 pm ]
Post subject:  Sanding scratches, a little tear out, and coloring Alder
First, I've been wrestling for a while with sanding end grain. I know there doesn't seem to be any shortcuts with dealing with it, but I always end up with scratches that look like this. (That's sanded to 100 150 180 220)

Attachment:
file-16 (002).jpeg


They disappear when I wet the wood with naptha. But I'm unsure if that's just what endgrain looks like after being sanded to 220, or if I haven't done enough.

Second, I got a little tear out in a few places that looks like this after sanding.

Attachment:
file1-5 (002).jpeg


I assume there's not really much to do other than either keep sanding, or use some filler? If I do use filler (glue and sawdust, or?) will that inhibit dyeing the wood?

Which brings me to my last question. I like the look of dyed wood as opposed to using colored toners, but is it a fools errand to try and dye an alder body? I've read that Alder doesn't take stain so evenly. I will of course practice my finishing schedule on scrap first, but like to be as prepared as possible at the outset.
Author:  Chris Pile [ Wed Oct 02, 2019 4:45 pm ]
Post subject:  Re: Sanding scratches, a little tear out, and coloring Alder
There is a reason why alder (and poplar) were usually painted solid colors.
Author:  Glen H [ Wed Oct 02, 2019 7:05 pm ]
Post subject:  Re: Sanding scratches, a little tear out, and coloring Alder
I’ve used a product called Minwax Pretreat that is excellent for making woods that don’t stain even stain evenly. It’s cheap, comes in quarts and so you can test it on scrap to see if it works for alder.
Author:  rbuddy [ Wed Oct 02, 2019 8:24 pm ]
Post subject:  Re: Sanding scratches, a little tear out, and coloring Alder
Looks to me, by your pictures, that the problem probably isn't all end grain related, but it is hard to tell exactly what we are looking at in the pictures. For the sanding process to work through the grit sizes, you have to eliminate previous imperfections at each level of grit change. Both your pictures look look like that has not happened.

The first pic looks like 100 grit or courser sanding scratches are still evident and the second picture shows obvious cross grain scratches that have not been removed by sanding at any grit level.

Every grit change must remove both imperfections, and the scratches left by the previous sanding grit, no way around that.

Sanding through the grits is a PITA and near impossible to get around.

About the only shortcut is power sanding where you can vary pressure and "simulate" a finer grit.

I also find a sharp scraper helps to get there quicker even on end grain.

Brian
Author:  Conor_Searl [ Wed Oct 02, 2019 11:51 pm ]
Post subject:  Re: Sanding scratches, a little tear out, and coloring Alder
rbuddy wrote:
The first pic looks like 100 grit or courser sanding scratches are still evident and the second picture shows obvious cross grain scratches that have not been removed by sanding at any grit level.


Yeah the first picture definitely could be 100 grit scratches. I started with that, and thought I got rid of them until I'd blown off all the dust. I understand the technique of sanding through grits in theory, but my experience is still not extensive. So I'm never really sure when I'm done with a certain grit and its time to move on to the next.

The cross grain scratch in the second picture I'm pretty sure was some tear out. Inside the horn was super rough after routing. I think I'd left too much material in that part of the guitar and when I routed it I tried to hog it all out in one go. So that's what's left after sanding through the grits.
Author:  B. Howard [ Thu Oct 03, 2019 7:36 am ]
Post subject:  Re: Sanding scratches, a little tear out, and coloring Alder
The tear out is left from routing the body, gotta keep sanding or that spot will show big time with or without stain.

The end grain looks very coarse. Gonna guess your using a drum sander. Looks like to much pressure while sanding and maybe the paper was a bit clogged. FWIW I quit all machine sanding at 180 and do my 220 final prep by hand.

Alder is a very lousy wood to dye. Not just the blotchies (which wood conditioner can help...) but the undistinct grain patterns get lost in the dye so even if it isn't blotchy it will look very bland and undefined..... Toners do not soak in and do not block out the grain like a dye.
Author:  Conor_Searl [ Thu Oct 03, 2019 11:29 am ]
Post subject:  Re: Sanding scratches, a little tear out, and coloring Alder
B. Howard wrote:
The tear out is left from routing the body, gotta keep sanding or that spot will show big time with or without stain.

The end grain looks very coarse. Gonna guess your using a drum sander. Looks like to much pressure while sanding and maybe the paper was a bit clogged. FWIW I quit all machine sanding at 180 and do my 220 final prep by hand.

Alder is a very lousy wood to dye. Not just the blotchies (which wood conditioner can help...) but the undistinct grain patterns get lost in the dye so even if it isn't blotchy it will look very bland and undefined..... Toners do not soak in and do not block out the grain like a dye.


Thanks Brian!

I think I came to the same conclusion as what you suggest about sanding with too much pressure as I was reading online about sanding end grain last night. I wasn't using a drum sander, but was getting a little annoyed and figured a little more elbow grease ought to get rid of my scratches, so I was working the wood pretty hard. It's back to the garage for me, a cup of coffee, some tunes, and a free couple of hours is the trick I guess.

I'll take your advice into account as well about the toner vs. dye. I'll try the wood conditioner and dye on some scrap, but I'll be prepared to spray...
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