Shellac query?

[woodbloke]

I'm in the process of polishing my SS gift using some blonde shellac dissolved in ordinary meths. After the first few coats, the finish turns white and then eventually after a lot more coats, the whiteness disappears...can anyone explain why? Does the temp of the 'shop (unheated) have anything to do with it? - Rob

 

[Chrispy]

I've never made my own polish but I think the problem may be the meths your using, the whiteness may be the minerals in the additive thats in meths, you should be using clear finishing spirit, (industrial alcohol) ccasion5:

 

[Ian]

I mix my own shellac and have never had this problem, could be some sort of reaction to the meths. I use clear alcohol - works very well and no nasty smell.

HTH

Ian

 

[CHJ]

Rob, is it by any chance moisture, humidity on surface at time of application or absorbtion by the meths, letting the jar stand open when not in use?

I have recently disposed of a gallon of 'meths' that had absorbed (not the correct word but can't think of the term) so much water that it would hardly ignite because of the low percentage of volatiles.

 

[MIGNAL]

I'm in the process of polishing my SS gift using some blonde shellac dissolved in ordinary meths. After the first few coats, the finish turns white and then eventually after a lot more coats, the whiteness disappears...can anyone explain why? Does the temp of the 'shop (unheated) have anything to do with it? - Rob

I brush on coats of Spirit Varnish (essentially Shellac). I've noticed this frequently. In fact when I first saw the 'whiteness' it was quite alarming, especially since it's supposed to be a clear(ish) finish. Within 10 minutes or so the effect disappears, as the Shellac dries.
It can't be directly because of the temperature. My workshop is warm and humidity controlled. I'm fairly certain that it has something to do with moisture though because it has a similar appearance to moisture trapped under shellac. That effect is common on Guitars that have been French Polished, the Players arm transferring sweat/moisture to the finish.
The solvent contains a very small amount of water (they all do) and/or it's a form of condensation. My guess.

 

[studders]

You can get a similar effect when spraying cars etc. It's called Blooming and is usually due to humidity/damp.

HTH

 

[Matt@]

if the finish is white, play a hair dryer on it. If the white is caused by moisture, you should see it disappear as the hair dryer heats the surface up. Make sure dryer isnt too close to surface of polish or it'll pickle!

 

[SeanJ]

trying to stay on topic here: what are the alternatives (that you can purchase) other than using Meths to make your own french polish then, anyone?

Sean

 

[yetloh]

I always use Morrells finishing spirit. It is alcohol with a small anount of shellac added. I've never had any problem with it.

Jim

 

[MIGNAL]

or Fiddes finishing Spirit - which is Ethanol with a small amount of added Shellac.
Not a lot wrong with Meths though.

 

[woodbloke]

Thanks for all the replies...it's almost like a white 'bloom' or very fine powder on the surface. Once I put some wax on it using a grey Webrax I suppose that cut it back a bit. Anyhoo, the finish has come up quite acceptable in the end. It occurs to me as well that it was a pretty old batch of polish that was a bit thick and 'gloopy' in the bottom of the jar, so dunno if that had anything to do with it - Rob

 

[MIGNAL]

Oh yes. The refined/bleached grades of Shellac (White, Pale) have a relatively short shelf life, perhaps 2 or 3 years in the flake form. They become difficult to dissolve in solvent, forming a gel like substance at the bottom of the jar. Almost like it's half dissolved. Fresh flakes will dissolve very quickly - overnight.
This doesn't seem to be a problem with the unrefined grades such as Button and seedlac. I have a batch of seedlac that is near 20 years old and still dissolves very readily.
Once mixed the shelf life is a matter of months. I usually don't let it go beyond 3 or 4 months.

 

[woodbloke]

Oh yes. The refined/bleached grades of Shellac (White, Pale) have a relatively short shelf life, perhaps 2 or 3 years in the flake form. They become difficult to dissolve in solvent, forming a gel like substance at the bottom of the jar. Almost like it's half dissolved. Fresh flakes will dissolve very quickly - overnight.
This doesn't seem to be a problem with the unrefined grades such as Button and seedlac. I have a batch of seedlac that is near 20 years old and still dissolves very readily.
Once mixed the shelf life is a matter of months. I usually don't let it go beyond 3 or 4 months.

That explains it, exactly what I had in the jar. It's as though the flakes didn't want to dissolve and became a bit jelly like and gloopy at the bottom of the jar...thanks for the explanation, much appreciated as I couldn't understand where the whiteness was coming from - Rob