• Beware of Counterfeit Woodturning Tools (click here for details)
  • Johnathan Silwones is starting a new AAW chapter, Southern Alleghenies Woodturners, in Johnstown, PA. (click here for details)
  • Congratulations to Paul May for "Checkerboard (ver 3.0)" being selected as Turning of the Week for March 25, 2024 (click here for details)
  • Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.

Sanding sealer

Joined
Jan 21, 2020
Messages
76
Likes
8
Location
Carlsbad, California
Why use sanding sealer? I’ve read several articles about its use and many say it’s not necessary if you are going to apply a finish which also seals the wood. So I was hoping someone could tell me why & how they use it and what they think it accomplishes that most other finishes don’t. Thank you.
 
Joined
Sep 27, 2017
Messages
396
Likes
204
Location
Windsor, Pennsylvania
I make a lot of small items to be painted. Unless there is a sealant, particularly on bass wood or poplar, the paint job looks like crap. Seal first and then paint & looks good. I don't use it for things that will not be painted. WOP works well too. The items are sealed on the lathe, set aside to dry for a day and then painted.
 
Joined
Jun 6, 2018
Messages
1,948
Likes
996
Location
La Grange, IL
I think the name "sanding sealer" is a misnomer. The purpose of this surface coating is to level out the microscopic gullies in the woods surface with a material that itself can be sanded to remove the microscopic peaks. It provides for a smoother surface than was achieved by sanding bare wood alone. Further coatings, such as varnish or paint can then be applied over this initial surface coating. In the paint example this can help prevent the grain pattern from telegraphing through, with varnish it will leave the surface smoother to the touch.

Sanding sealers do not really seal any more than any other surface coating. All coatings provide some barrier, some more than others, but nothing short of molten plastic is impermeable to water vapor. The only place where sanding sealer may in fact provide for some sealing is when dye stain is applied after the sealer. I believe that some of the dye will penetrate, but sealer may modulate how much and where. I think there may be an effect with pigment stains, as well, but I'm not sure.

Sanding sealer is most commonly a dilute (1 pound cut) of shellac, which has the advantage that shellac adheres to all other coatings. I believe there are sanding sealer products based on lacquer, as well. A good resource on finishes (surface coatings) is Flexner's book, Understanding Finishes.
 
Last edited:
Joined
Oct 23, 2015
Messages
210
Likes
288
Location
Springdale, Arkansas
No, I use a vinyl lacquer sanding sealer. The reason is it drys in seconds, easy to wipe on with the turning in the lathe, and improves water resistance of lacquer top coats. It also enhances defects such as tool marks, tear out, and scratches so I can see/correct them before finishing. I use it no matter what final finish I use.
 
Joined
Jun 6, 2018
Messages
1,948
Likes
996
Location
La Grange, IL
Vic, another trick is to wipe with mineral spiriits before applying coatings. This mimics what the finish will look like and brings out blemishes before you're committed to coatings. It also removes any remaining sawdust.
 
Last edited:
Joined
Jan 21, 2020
Messages
76
Likes
8
Location
Carlsbad, California
Thank you, so I guess by the answers so far it doesn't really make minor tool marks and tear out easier to deal with. Just helps to provide a microscopicly, (if there is such a word), smoother finish and feel once it is smooth to the naked eye. Correct maybe?
 
Joined
Jun 16, 2004
Messages
1,224
Likes
1,134
Location
Colorado Springs, CO
I've had good results using sanding sealer before painting. Never been able to get a finish like this without the sealer:
gallery_hero_9ea78154-53de-45b0-8863-340a2cf01647.jpg

b8faea31709c6d628ff939b3bdeb6289.jpg
 
Joined
Jan 21, 2020
Messages
76
Likes
8
Location
Carlsbad, California
Amazing. You guys say you use it, but how. Apply a coat before every grit of sanding, only before the last grit or after all sanding is done? I guess in other words how do you use it.
 
Joined
Mar 17, 2006
Messages
213
Likes
96
Location
Canton, Connecticut
Another "non-finishing" use for sanding sealer is the following:
If you need to do a repair on a piece, for example filling a crack (with sawdust, metal powder, coffee grounds, etc.) and applying CA glue, the CA will stain the wood and be very difficult to sand out. If you use sanding sealer before doing the repair, any stains from the CA will readily sand out.
 
Joined
Sep 27, 2017
Messages
396
Likes
204
Location
Windsor, Pennsylvania
I think the name "sanding sealer" is a misnomer. The purpose of this surface coating is to level out the microscopic gullies in the woods surface with a material that itself can be sanded to remove the microscopic peaks. It provides for a smoother surface than was achieved by sanding bare wood alone. Further coatings, such as varnish or paint can then be applied over this initial surface coating. In the paint example this can help prevent the grain pattern from telegraphing through, with varnish it will leave the surface smoother to the touch.

Sanding sealers do not really seal any more than any other surface coating. All coatings provide some barrier, some more than others, but nothing short of molten plastic is impermeable to water vapor. The only place where sanding sealer may in fact provide for some sealing is when dye stain is applied after the sealer. I believe that some of the dye will penetrate, but sealer may modulate how much and where. I think there may be an effect with pigment stains, as well, but I'm not sure.

Sanding sealer is most commonly a dilute (1 pound cut) of shellac, which has the advantage that shellac adheres to all other coatings. I believe there are sanding sealer products based on lacquer, as well. A good resource on finishes (surface coatings) is Flexner's book, Understanding Finishes.

Sanding sealer generally uses unwaxed shellac, because the shellac with the wax does prevent some finishes from adhering well. It may not seal the wood, but when I follow it with latex paint, the paint goes on smoothly, doesn't cake flake or raise more whiskers.
 
Joined
Sep 27, 2017
Messages
396
Likes
204
Location
Windsor, Pennsylvania
Thank you, very helpful.
I do something similar. Sand to 400, apply the sealer, but since my items are small, I don't re sand. I make lots of Christmas tree ornaments for charity. Bright colors, a bit of shine, but they are not handled that much, like YoYos and some other items. That is also why I use cheap easy to turn woods like bass and poplar. very easy to sand out blemishes compared to maple or fruit wood.
 
Joined
Jul 19, 2018
Messages
1,686
Likes
2,077
Location
Ponsford, MN
WOP works well too. The items are sealed on the lathe, set aside to dry for a day and then painted.
Hey you should not be using derogatory terms for Italians. OK if WOP means wipe on poly that would not be compatible all possible top coats, however shellac is.
Another "non-finishing" use for sanding sealer is the following:
If you need to do a repair on a piece, for example filling a crack (with sawdust, metal powder, coffee grounds, etc.) and applying CA glue, the CA will stain the wood and be very difficult to sand out. If you use sanding sealer before doing the repair, any stains from the CA will readily sand out.
The best thing to use when filling cracks or voids with powered stone or the other inferior (in my opinion) materials listed is a light cut of shellac and the purpose is to prevent the CA from sealing the surrounding wood and thus affecting the appearance of the final finish.
 
Joined
May 4, 2010
Messages
2,432
Likes
1,846
Location
Bozeman, MT
Thank you, so I guess by the answers so far it doesn't really make minor tool marks and tear out easier to deal with. Just helps to provide a microscopicly, (if there is such a word), smoother finish and feel once it is smooth to the naked eye. Correct maybe?
No, sanding sealer will not remove or make your tool marks and tear out easier to manage. I don't paint things and almost never use sanding sealer. If I wanted a glass smooth surface on a project, a 'museum quality finish', I would use sanding sealer.

Getting rid of tool marks and tear out is a perennial and lengthy topic. The basic answer is to sand a lot until you get better enough not to cause those problems.
 
Joined
Jul 10, 2017
Messages
824
Likes
665
Location
Windermere, British Columbia
2434C1F6-4808-4D72-93B3-ECFBBDDA019F.jpeg
Why use sanding sealer? I’ve read several articles about its use and many say it’s not necessary if you are going to apply a finish which also seals the wood. So I was hoping someone could tell me why & how they use it and what they think it accomplishes that most other finishes don’t. Thank you.
A very good answer to what is sanding sealer and when to use!
 
Joined
Sep 27, 2017
Messages
396
Likes
204
Location
Windsor, Pennsylvania
What brands do people use? Are all brands the same? Thanks!
I use Zinsser's Seal Coat. Getting hard to find. There is now a water based sealer, but it raises the grain too much for my use. Zinsser's seal coat is getting hard to find in these parts. Not at Lowes, Home Depot, Ace Hardware, Got mine at a True Value Hardware store that has since closed. I did find a qt of wipe on lacquer at my local Lowes. marked down to $2. It dries almost before it is applied to the item. Really lots of fumes. Found it works better for dipping items in it.
 
Joined
Feb 6, 2010
Messages
2,959
Likes
1,905
Location
Brandon, MS
Shellac can be used as a sealer but is not sand and sealer. As the article stated sand and sealer has stearates in it and according to Flexner this process was invented by the furniture industry in the late 1800's and the purpose to make sanding easier because it makes a soft finish. Anytime you use sand and sealer you have places a coat of a softer finish under your hard surface finish and it will dent or scratch easier per Flexner.
 
Joined
Apr 13, 2017
Messages
267
Likes
140
Location
Gainesville, VA
I rarely use a sanding sealer, however, when I do use it I use a lacquer sanding sealer cut 50% by lacquer thinner. Does a fine job and dries lickety-split.
 
Joined
Jul 19, 2018
Messages
1,686
Likes
2,077
Location
Ponsford, MN
I have never used sanding sealer on turnings and when I want to achieve a glass smooth finish I spray unthinned lacquer and sand between coats. The open pores will show up as shiny spots after the sanding so when those spots don't show up it is time to polish the finish to restore the gloss.
 
Joined
Nov 16, 2010
Messages
15
Likes
1
Location
Lewistown, MT
I rarely use a sanding sealer, however, when I do use it I use a lacquer sanding sealer cut 50% by lacquer thinner. Does a fine job and dries lickety-split.
I remember hearing Bert Marsh at the 30 th Anniversary of the Utah symposium in a demo saying that he did the same thing with a 50-50 mixture of nitrocellulose lacquer and thinner. I’ve been doing the same
And I like most of the time.
 
Joined
Sep 27, 2017
Messages
396
Likes
204
Location
Windsor, Pennsylvania
thats fine for items that won't be painted. I found with lacquer that some of the paints run and bleed terribly. I use oil paint pens for detail and striping. Sort of like magic markers but with oil paint. They work great over Zinsser's Seal Coat, fine over WOP, but bleed something awful when used over lacquer.
 
Back
Top