Sanding Sealer Question

[Dizzwold]

Hi Guys,

I have some walnut I'm using for pelmets around my living room.

I'm sanding them back with 80, 120, 240 grit then finishing with 0000, Chestnut Cellulose Sanding Sealer and burnishing again with 0000 wirewool.

On one length I'd completed with the above process, I've had to sand part of it back to bare timber.

If I recoat the bare timber with the sanding sealer, will it create a tide mark where the fresh coat of sanding sealer meet/overlaps the existing sanding sealer?

Would I be better off to just sand the full length back and recoat with sanding sealer?

Dizzwold.

 

[Phil Pascoe]

I'd think you are working for nothing going beyond 240. No, you shouldn't get a line, especially if you've thinned the sealer which is always a good idea - I thin it 50/50 with cellulose thinners
Try using hot water - pour on, wipe off, go to lunch or knock off and leave it dry. It's surprising how much grain it'll raise, it can't do any harm and leaves no marks. Of course, you can do it between grits as well. Always worth a try, it's free.

 

[Blackswanwood]

I doubt you will create a tidemark I think I would wipe the dry edge of the already applied sanding sealer with meths using a lint free cloth immediately before applying to the adjoining piece. (That assumes it’s shellac based sanding sealer)

 

[Phil Pascoe]

He's using cellulose.

 

[Blackswanwood]

He's using cellulose.

Ah yes - sorry - as the youngsters say “my bad”!

 

[johnnyb]

No it won't have quite the same build but each coat of cellulose melts into the last and is the reason its usually sprayed if multiple coats are used as it drags.

 

[Dizzwold]

Hi Guys,

Thank you for your replies. I'm very grateful.

Can any of you explain what has happened to this piece. This has had the exact same process as previously explained (sanded with 80, 120, 240 grit, 0000 wirewool, sanding sealer and burnished with 0000 wirewool again).
The only difference with this and others I'd already made, is this piece was straight from the timber yard that morning and worked on that same day?

The sanding sealer went On as normal (not pooling or anything odd), but when I went back to it it looked liked I'd missed areas. So I recoated these parts again. Again this looked fine and normal, but later, yet again it looked liked I'd completely missed these areas?

 

[johnnyb]

Not sure but is it sapwood? Pale wood from outside of the tree.

 

[Nelly111s]

It’s probably worth asking Terry Smart at Chestnut finishes. He’s very helpful. He publishes a weekly newsletter (yours may get featured) where he answers questions regarding different finishes.
And, by the way, don’t thin the sanding sealer - it’s the right consistency out of the tin (ask Terry - he’s a chemist).

 

[Phil Pascoe]

If it's the right cosistency out of the tin I'd suggest buying a better one, it'll work out cheaper.

 

[Dermot McArdle]

The problem might be that you are considering the the use of cellulose sanding sealer as a finish in itself. It is only a sealer and is a base on which to apply a further decorative finish such as wax or a clear lacquer.

Traditional wood finishers prefer to use shellac sanding sealer which has a high build quality, so filling some of the wood grain and settling to an even low gloss finish in itself.

Both sealers do require the dried finish to be sanded back flat in order to achieve an even effect. I would try using 00 wire wool instead as the 0000 is only useful as a polishing agent.

With your sample, try rubbing on a further coat of sealer with a folded cotton pad. If the dull patch persists, rub on some clear wax, it should disappear then.

 

[scooby]

Terry used to post here, but I don't think he's be on for a while. I recall he was pretty helpful when I had a sanding sealer issue with a turned item (which was also walnut, but the issue was different). After that, I always oil (usually some type of hard wax) on anything walnut.

As for thinning sealer, I always used un thinned..only because I kept forgetting to buy thinners. I used to watch a lot of turning stuff on YouTube, a lot. I'd say 99% were thinning the sealer.

 

[Jake]

It just looks like that is much more porous / absorbent, does look rather like sapwood like Johnny said. Give it some more coats and it'll stop sucking it in after a while.

 

[Fergie 307]

I suspect it is some kind of contamination. It could be blooming, which is usually down to excess humidity or too low temperature when spraying. Could just be a bit of excess moisture in the wood itself.
Hard to see in the picture but if the effected areas have even a slightly milky look, then blooming is probably the answer. Can often appear on thicker parts that remain colder for longer.
Remedy is to rub back then either remove the problem, so warmer drier environment, or use anti bloom thinner.

 

[Hypnotic Chimera]

Newbie input/question!

Isn't the idea behind sanding sealer that it gets absorbed into and fills out any porous areas, so that when you sand the sanding sealer back to bare wood prior to applying a finish, the sanding sealer is blocking the pores, so to speak, and those ares won't absorb any finishing product, like they might have had you not used sanding sealer, thereby helping to provide a uniform coating and even finish?

If that area has absorbed the sanding sealer, then isn't that a sign that it's doing its intended job?

 

[Dizzwold]

Hi Guys,

Thank you for all your comments.

Just to clarify, this is Superior Grade Black Walnut from Whitmores Timber, 'Neat' Non-Thinned Chestnut Cellulose Sanding Sealer Applied with a Synthetic Brush. When I took these photos, these areas that look like I'd missed patched, have had 2 coats of SS, yet still look untouched with SS.
https://www.axminstertools.com/ches...0473?queryID=6031db73fb1e504616e2a7f4db8bdb29
https://www.axminstertools.com/chestnut-microcrystalline-wax-951143
Once the problem is resolved it'll be burnished back with 0000 wirewool, finished with Chestnut MC Wax, like the ones previously made.

I didn't have this problem with any of the others I've already made, but these where done when the UK weather was warmer and drier. Also the previous walnut had been stored inside the house for a few days 'or more' prior to any work, and all the work is done outside in the elements (no shelter).

So maybe it's due to the timber being wetter (fresh from the timber yard that very day), temperature and the dampness?

I've sanded it back and brought it into the house. I'll perhaps apply the sanding sealer inside the house being that it's one of the shorter ones. I'll see if I can get it done by the weekend and keep you posted.

 

[johnnyb]

Sanding sealer basically does what most initial coats of finish do and that is to raise the grain. So the surface becomes rough. The difference with sanding sealer is it contains a stearate soap(cellulose and shellac but they do have to be vigorously shaken) this stops the sandpaper getting clogged and provide a nicer smoother surface albeit softer than coat on coat which will be harder. So most people are sealing, sanding but using other products as topcoat.

 

[the great waldo]

Sanding sealer basically does what most initial coats of finish do and that is to raise the grain. So the surface becomes rough. The difference with sanding sealer is it contains a stearate soap(cellulose and shellac but they do have to be vigorously shaken) this stops the sandpaper getting clogged and provide a nicer smoother surface albeit softer than coat on coat which will be harder. So most people are sealing, sanding but using other products as topcoat.

Finishes don't raise the grain unless they are water based. You can raise the grain with a damp cloth on raw wood (best to sand it lightly after its dry with 320 or similar fine abrasive) The sanding sealer is as Johnny b says a laquer/finish with filler powder to build up laquer thicknes before going onto the more expensive top coats which tend to contain more solvents and the stearate helps lubricate with sanding.
Cheers
Andrew

 

[Jake]

Just to clarify, this is Superior Grade Black Walnut from Whitmores Timber

Sapwood is not necessarily a defect in black walnut, they often steam it to make it look more even in colour. I think you'd need to know the exact grading criteria that Whitmores (or rather their suppliers) use.