Sanding sealer use or don`t

[Ron Booth]

I have read many threads about using SS. They all have been very useful. However , I have spoken about the problem of long dryingtime and "Glugging" when sanding with the "Haymes" man and he just says to use two coats of whatever "varnish" I hadplanned to use with a light sand in between and forget the Sanding Sealer.
Does anyone have a good and proper reason for using or needing Sanding Sealer.
Ron B

[Dion N]

Not sure what you mean by "long drying time." Sanding Sealer is (or should be) mostly metho and a little bit of shellac. The metho evaporates off in a few minutes and I usually sand after 5 or 10 minutes.

[watson]

The tins that you buy of "sanding sealer" lean more towards being "pore fillers".
I cut shellac 6:1 with ethanol and use that after sanding ....depends on what's happening.....to say 400.
Let it dry.....sand with the grain with say 1200 wet & dry.......which removes the "hair" stuck up by the diluted shellac.
I then finish sand to whatever.

[powderpost]

Sanding sealer is really a clear grain filler. I use a fair bit of it to fill grain on jobs that have a number of different coloured woods, to get a "glass" like finish. In days gone by, grain fillers were made from whiting, turps and a colouring agent, to match the timber colour, not good with multi coloured timber projects. The whiting in the older grain fillers, shows up as small white flecks in the grain on some very old pieces of furniture during restoration. Clear grain fillers (sanding sealer) are often spirit based and dry very quickly eg 30 minutes. After sanding back, the final finish can be applied. Does that help?
Jim

[dr4g0nfly]

I tend to agree with what's been said above. For me I use SS if all I am going to finish with is wax (Arts & Crafts style), I prefer not to use it if I am going to apply another type of finish such as varnish and certainly not with spirit based stains (learnt that one the hard way).

Having said that I notice that you talk about SS as being different to what I use. Here in the UK it is normally a Cellulose based product with wood flour, certainly not the shellac based product that seems available in Aus.

[bookend]

My understanding is that there are 2 types of sanding sealer. One simply raises the grain so the hairs can be sanded off and the other is a grain filler as well as a sanding sealer in that it fills gaps and raises the grain hairs.

The shellac/ ethanol mix is an example of the former and is quick and easy to apply. Feast Watson Sanding Sealer is an example of the latter and opinions vary on the results achieved. It takes longer to dry and can be prone to "glugging".

[Ron Booth]

Thanks for all of your comments. The SS I used was Feast Watson from a 1 litre can which was one year old and was still 80% full. The drying time was more than 2 days. The project was in my garage where the ambient temps were 7-8 overnight and 17-20deg C in the daytime. As I failed to say, I gave up and washed it all off with Turps and will now start again using oil based polyurethane, thinned about 10% with turps ; a couple or three coats and then a beeswax cut with steel wool.
An interesting note from the Haymes man--water based polyurethane will prevent Huon Pine (and I guess many other woods) from yellowing, but the oil based will allow it to mellow to what we all like as the warm colour of aged Huon Pine.

[Mr Brush]

Yup - I also made the mistake of buying a 'commercial' SS, Feast watson I believe.

Unfortunately I then tried to use it in the manner suggested in most books on finishing, including the excellent volume produced by our fearless leader (Neil). The Feast Watson SS had a very 'gluggy' consistency (after about 15 mins of vigourous stirring to get rid of the solid lump in the bottom of the can...), could only be applied in a fairly thick coat, and was clearly not designed to just seal and raise the grain before a final sanding. When the stuff finally dried (!), I ended up sanding it all off and vowing never to use it again.

Fortunately I then tried the Ubeaut Sanding Sealer, which is of the traditional thinned shellac type, with excellent results. These days I tend to just thin down Ubeaut White Shellac when I want a SS, which works just as well.

I'm sure the Feast Watson SS has a use somewhere, but it certainly doesn't work as a sanding sealer in the traditional sense.

[durwood]

Sanding sealer is designed to do what the name implys - seal.

Its intended to be applyed before a coat of material which would otherwise soak into the wood. As most finishes are good quality and therefore expensive then it makes no sence using them if they just soak into and disappear in the timber. Conversly if you seal first its not easy to apply some coating such as stain which are designed to soak into the timber. In that case you stain (fill also if needed) first then seal off.

Sanding sealer is designed to coat the wood and seal it off so the following coating can do their job of providing a protective coating on top of the timber.

Shellac works so well because it only dissolves in ethanol and dries very quickly. virtually any other finish will have a different solvent so will not dissolve it and therefore just dry on top. If you are putting more shellac on top the fast drying prevents too much dissolving and soaking in of the material.

Some paint suppliers have sealers which use turps as their base and when they dry they harden and don't redissolve so when you then add a turps based product it can't soften it and soak into the timber -therefore it has sealed!! only trouble is it dries slowly, can have a short storage life and if used with the wrong top coating end up in a mess. You should always check that the sealer you buy is Ok for the next coating you are putting over it.

As mentioned before shellac is so different that virtually any top coat will not attack it so if you use it as many have suggested you should never have a problem sealing off the timber if you deem it necessary to do so.

The lacquer and enamel based sealers have filler in them to help get a smooth surface usually "sanding' in the description means it will fill somewhat and help you get a smooth surface quickly and in a lot of cases get rid of the need to fill the timber grain. Whatver is put onto the bare timber will tend to raise the grain as there are always loose grain particles which will raise up. sealer or no sealer the first coat of any coating raises the grain and you would normally give it a wipe with a sandpaper to remove the rough texture.

After that whether you get a smooth surface or not depends on the products you use the number of coats applied to fill the uneven surface and how well you may have sanded betweeen coats and applied the finish.

Some sealers are meant to apply in a wet coat then allowed to dry and must not be sanded before the next coating is applied. So unless it says "sanding sealer" don't sand it. The instructions should say this anyway.

[Ron Booth]

Thanks to Mr Brush and Durwood. You have explained the position really clearly and I will now go over to white shellac and consider myself a winner.
My last word on the Feast Watson SS--As a desperate effort I wiped it on a scrap with a clean (ish) rag and then wiped most of it off. It dried in less than 6 hours and was sandable without glugging. RB
Clearly though it did not provide much filling.

[The_Fixer]

Thanks for all of your comments. The SS I used was Feast Watson from a 1 litre can which was one year old and was still 80% full. The drying time was more than 2 days. The project was in my garage where the ambient temps were 7-8 overnight and 17-20deg C in the daytime. As I failed to say, I gave up and washed it all off with Turps and will now start again using oil based polyurethane, thinned about 10% with turps ; a couple or three coats and then a beeswax cut with steel wool.
An interesting note from the Haymes man--water based polyurethane will prevent Huon Pine (and I guess many other woods) from yellowing, but the oil based will allow it to mellow to what we all like as the warm colour of aged Huon Pine.

Not sure if I'm on the right track here, but arren't most painting products temperature sensitive. Most products don't like going under 10 degrees C.

I painted a cupboard one winter's night up here and left it to dry overnight. It was a cold night and the paint never dried properly. Had to make sure it didn't get too cold for a while afterwards and all was fine.

[durwood]

You are right, if its too cold you slow down or stop the drying process.

The paint manufacturers make the paint for normal conditions that people would paint in. so if its too cold or too hot it affects the drying time. Solvents needs to evaporate heat makes them do this.

Heat even helps the chemical reaction in 2 pack paints, if you mix the hardener into the paint you will normally have about 6 hours depending on the material. If for some reason you then find you don't or can't apply the mixed paint you can seal it up in a tin and put it in a fridge. It will be OK to use 24 hours later just let it get back to room temperature and you still have most of you 6 hours to apply it.

A friend told me about a demo of a new process which was conducted in Melbourne on a cold winter morning. the paint would normally dry in 7 minutes by chemical reaction (reason for the demo) and it was still wet after 30 min. The chemist was in a panic when it was suggested by the painter it was cold he brushed off the comment. Eventually he was convinced to try it. They warmed up the room with a heater did the demo again and it worked how it was meant to be.

If you live in a cold climate the paint would be adjusted for that by the paint company. In some cases fast drying paints such as lacquers have different thinners for winter and summer ( here in Australia) or you can purchase additives to change the drying time (slow down in summer speed up in winter)

Generally most of the year the temperature is between 15C and 25C, the instructions on the tin usually state approx drying time for normal temp and often warn against using below 15C.

[The_Fixer]

Incidentally, when the day warmed up after that cold night, the paint still wouldn't dry. I had to strip it off and redo it.

All went well then...