Hallo Karl,

willkommen im Forum.

Das Ansäuern mit Salpetersäure dient in erster Linie dazu, das Email etwas härter zu machen, d. h. den Schmelzpunkt leicht zu erhöhen. Das ist normalerweise nicht erforderlich. Opake Emails kann man so verwenden, wie sie vom Hersteller kommen. Transparente Emails müssen, wenn man klare, transparente Farben bekommen möchte, entweder gewaschen, oder der Feinanteil muss ausgesiebt werden.

Edmund

http://www.emailkunst.de

Hi Karl

You don´t need to do this everytime you want to use enamel.Some people use this procedure to "refresh" the old, long time stored enamel.You need also wash the enamel after acidulation that the acid will not affect the enamel when fired.

Maybe more skilled enamelers have better advice about this.

R.

Das is interessante.Schmelzpunkt erhöhen mit Säure.Funktioniert es mit roten,gelbe und andere warme Farben? Wie viele Tropfen?

Danke schon

R.

Hallo Rudolf,

die Schmelzpunkterhöhung ist marginal. Es macht vielleicht 5-10 Grad C aus. Soweit ich weiß, funktioniert es mit allen Farben. Auf 10 Gramm Email sollten 5-10 Tropfen konz. Salpetersäure genügen. Ob es auch mit bleifreien Emails klappt weiß ich allerdings nicht.

Edmund

Das is nicht so gross Unterschied,aber danke schon Edmund.

R.

 

Thanks a lot, Edmund and Rudolf. That made things quite literally a bit clearer.

Hello Karl!

It's good to see you here, I have seen examples of your enamels on the other forum and they look great, so you should be here. I hope you will post some photos. Your experience and knowledge will be invaluable here.

I ended up here because someone gave me about 25 pounds of old enamels and I needed to know if they were lead-free or not. I haven't done enameling for years, but am getting interested again.

Thank you for your help in the past.

Debbie K

Hello Debbie,

good to see you around here too and thanks for your kind words. I am really glad I have found this community here as I am still comparably new to enamalling... there is so much to learn about this technique.

25 pound of enamel is a nice bit of stuff. I am looking forward to see your work using it and how it will match your stone carvings. I am sure it will be very cool stuff.

Hello Trish,

thanks for your advice. I think I will skip the acid when it comes to enamel powder.

Regards,

Karl

Hi Karl,
so as Trish wrote Nitric-acid is absolute unnecessary if you use fresh enamels.

In earlier time the compositions of enamels were not so good, stable and uniform.
So it could happen, that enamels, which was stored in powder-form for a longer time and in a wrong athmosphere became oxidized. If one uses such enamels, after firing the enamels were cloudy and it could happen, that onto the fired surface lay a fine white shift.
To refresh those bad emails, one poured in some drops of nitric-acid into the powder. So the most of the oxidized material becomes resolved. After washing the enamels were useable again.

Edmund

You might also consider grinding the older enamels up gently in a mortar and pestle. this would break off the outside of the grains, which would then be washed out during rinsing after the grinding. 

Ricky:

Wouldn't that make the transparents more opaque? I've always understood that the finer transparents were, the more likely they are to become cloudy.

I'm really interested in this thread as I have both old enamels and nitric acid (and no fear of using it). I might try both to see which works better and I will post results if I do.

Debbie K

Science of Color Transparency Principle #1: Air bubbles within the glass creates a cloudy look. The finer the grain size of the enamel, the more air bubbles. 

Science of Color Transparency Principle #2: The thicker the layer of enamel, the more air bubbles.

So it follows that for maximum clarity you would use larger grains of enamel and thiner layers. If you need to use finer particles you need to make sure that you use thin layers. In the case we're discussing, you would not have to change the size of the grains too drastically when grinding them. Just break them down a little to get rid of the outer edge of the grains. You don't have to reduce them too much. 

I just want to know: I have one pale blue enamel from W.G.Ball UK,there is always lots of bubbles.I tried use thin layers,lower temperature,washed properly,when wet packed I used vibrating pen to compact the grains together but the result is always the same.Acid and regrind this 80mesh enamel is the last thing I didn´t tried.Any other ideas please?

Thank you

R.

Hallo Rudolf,
I have the same problem with a transparent gray from Schauer. I mixed the gray enamel with about 10% of a soft flux. This mix don't produce so much bubbles as the only gray enamel, but it don't solved the problem realy.

Edmund

Hi folks,

For those who might be considering giving this method a try but haven't worked with acid, be sure to follow the adage "do as you ought to, add acid to water." (That rhymes if you live in the Boston area.) Adding water to concentrated acid creates a vigorous surface reaction that can result in spattering and a lot of heat. So I suggest you keep the following in mind:

Wear adequate eye and skin protection.

Be sure the enamel is wet before you add the acid.

Continue taking care when rinsing the enamel off.

Best Regards,
Herv

Hallo all,

this is my first post in this fine forum. I am a sculptor from Germany. I am not very experienced as an enameller.  So I may chime in with a question about the preparation of enamel powders. Is the acidulation of enamels still done today? I ve read about the addition of a few drops of concentrated nitric acid to the ground and wet powder in some older books.

Thanks in advance for your valuable input.

Best, Karl