Cellulose Sanding Sealer

[Saint Simon]

As a finishes beginner I have only just discovered cellulose sanding sealer. Up until now its been all hard wax oil and waxes. However, recently I have been very happy with the finished results on small pine boxes of just a coat of CSS applied with a brush which I then rubbed down lightly with very fine sand paper. Its quick, feels good to the fingers and has a nice look. But it feels too easy.
How am I going to come unstuck please?
Simon

 

[CHJ]

..How am I going to come unstuck please?
Simon

Only by sanding through the sealed surface in places and ending up with a blotchy surface if you apply a paste wax or similar.

If you are sanding to de-nib excessive raised grain you may need to give another coat to ensure a sealed finish.

A burnished Cellulose Sealer skin finished with a hard wax is all I use on nine out of ten pieces.

Look at my Bits & Pieces link or This pamphlet

 

[woodpig]

Don't use sandpaper Simon, just de-nib with 0000 wire wool and you should be fine. It's a great product in my view and although like many I have been thinning it a bit with cellulose thinners a professional turner recently advised me to use it neat so that's what I'll be doing on my next project.

 

[oakmitre]

The reason I use sanding sealer is to prevent grain raising when applying a waterbased finish.

If you are using an oil or solvent based finish you can use steel wool.

The tiny particles of steel wool left behind will flash rust and bloom in a waterbased finish.

The solution is to use a "Non woven hand pad", these look remarkably like a scouring pad, but they come in different colours.

A small piece of this can be use quite a few times before it wears out, but it does fill with dust so you have to keep cross contamination in mind.

They are however expensive.The Norton/Oakey brand can be picked up cheaper sometimes on ebay, Axminster sell Mirka which is a bit more.

The difference between normal scouring pads and the real thing is the particle size distribution of the abrasive (the scouring pads can contain random larger gritty bits),the rate of wear and also the very cheap scouring pads contain dyes(usually green) which can rub off.

Tesco value scouring sponges (40p for 8) are pretty useful and don't stain. I glue a piece of fine sandpaper to the sponge side and use the scouring side as is.I have found that if you coat a piece of scrap wood with the same sanding sealer then once dry rub the scouring side onto it, it can remove the risk of those large gritty bits before going to your work.You could try this to get a feel before splashing out on the proper pads.

Matt.

 

[thetyreman]

isn't sanding sealer just watered down shellac? what's the difference between shellac and cellulose sanding sealer?

 

[woodpig]

I've not experienced any problems with rust using wire wool but you can buy this if you do.

https://www.amazon.co.uk/dp/B000XBCSC4/ ... H7DAT9BH56

 

[Droogs]

Shellac is a secretion from the lac beetle used by it to form its incubator for its eggs. It starts off quite waxy and then dries out in the Indian sun, it is then processed into flakes and when dissolved in alcohol used by us.

Cellulose is the long chain sugar protein that forms the fibrous part of flora and when used in it's nitrated form becomes old fashioned varnish. A very thinned down version is used by woodworkers as sanding sealer.

hth

edit
re the rusting this is usually encounter when using high tannin content wood such as oak. the iron reacts with it causing the rust and black marks on the surface of the wood

 

[ED65]

isn't sanding sealer just watered down shellac?

Shellac sanding sealers are supposed to be that yes, but I just discovered two or three days ago that the one I've been using for years is a 4lb cut! That's the opposite of watered down :shock:

what's the difference between shellac and cellulose sanding sealer?

One's made from shellac dissolved in a denatured alcohol of some kind, the other presumably from nitrocellulose dissolved in some form of cellulose thinners/lacquer thinner (many variants of this).

The latter tend to evaporate even faster than alcohol so cellulose sanding sealers tend to dry really quickly.

In addition cellulose thinners are usually more pongy and the fumes are slightly more toxic than those from alcohol, even with the denaturing additives.

 

[Phil Pascoe]

Don't forget if you are worrying about water based finishes raising the grain, there is an answer. Use (hot) water or steam to raise the grain - then sand and polish. The beauty of using water is that if it does no good, it will do no harm. Sealers can sometimes cause blotchiness.

 

[thetyreman]

isn't sanding sealer just watered down shellac?

Shellac sanding sealers are supposed to be that yes, but I just discovered two or three days ago that the one I've been using for years is a 4lb cut! That's the opposite of watered down :shock:

what's the difference between shellac and cellulose sanding sealer?

One's made from shellac dissolved in a denatured alcohol of some kind, the other presumably from nitrocellulose dissolved in some form of cellulose thinners/lacquer thinner (many variants of this).

The latter tend to evaporate even faster than alcohol so cellulose sanding sealers tend to dry really quickly.

In addition cellulose thinners are usually more pongy and the fumes are slightly more toxic than those from alcohol, even with the denaturing additives.

yes a 4lb cut is very thick! I've just been learning how to make shellac and getting good results with 1lb cut, you'd expect a 1lb cut for a sanding sealer or even thinner like 1/2lb cut.

 

[ED65]

Sealers can sometimes cause blotchiness.

But shouldn't a sealing coat reduce that tendency rather than cause it?

 

[ED65]

you'd expect a 1lb cut for a sanding sealer or even thinner like 1/2lb cut.

Yep! You can use a wash coat or "spitcoat" of shellac as a sanding sealer and those can be mixed even lighter than a 1/2lb cut.

 

[custard]

As a finishes beginner I have only just discovered cellulose sanding sealer. Up until now its been all hard wax oil and waxes. However, recently I have been very happy with the finished results on small pine boxes of just a coat of CSS applied with a brush which I then rubbed down lightly with very fine sand paper. Its quick, feels good to the fingers and has a nice look. But it feels too easy.
How am I going to come unstuck please?
Simon

I'll leave aside the obvious stuff like degree of protection and say it really depends on your time frame.

Cellulose sanding sealer is a terrific finish for all the reasons you mention, but after a couple of decades it will look pretty tatty and need refinishing. If you're a commercial operation you probably couldn't care less about appearances in the year 2036, all that counts is showroom appeal. But if you're aiming for treasured heirlooms for friends and family you might take a different view.

The timber you're using also has a bearing on the decision. A fruitwood say, or Yew, or Walnut, or Rosewood, or a decent South American Mahogany, will all patinate given enough time to a something verging on the sublime. But if you have to strip and re-apply a cellulose finish every twenty or thirty years the clock will keep being re-set on that patination process. Beech, Ash, Oak, Sycamore or Pine will all age too but, at least to my eye, time doesn't bestow quite such a bounty on those particular timbers, so you could argue that refinishing doesn't cost quite so much in terms of lost patination.

 

[Phil Pascoe]

Sealers can sometimes cause blotchiness.

But shouldn't a sealing coat reduce that tendency rather than cause it?

Logically, yes, but on some woods it seems to.