I need some help. I'm a potter that uses zinc oxide in one of my specialty glazes. I also have a large amount of powdered zinc metal. I would like to
find a method to create zinc silicate from the powdered zinc or from zinc oxide.
I'm a potter not a chemist so what I have to start with are several raw materials. first the 2 forms of zinc, next some sodium silicate(water glass)
and have access to several common acids as well as soda ash.
What I would like to do is make a solution and through evaporation create zinc silicate crystals. I will then use these crystals in a glazes to act as
seeds to grow large zinc silicate crystals on my pottery.
I currently do this with the zinc oxide in the glaze but zinc silicate and the zinc oxide would give me a wider range to work with in my glazes.I hope
someone here might have an idea to help me develop these zinc silicate crystals.
Thanks for any thoughts on this.
Wyndham
Adas - 20-11-2011 at 12:37
Na2SiO3 + ZnCl2 ----> 2 NaCl + ZnSiO3
And before reacting Zn or ZnO with HCl, I recommend you to distill it. Technical grade HCl contains iron contamination.
[Edited on 20-11-2011 by Adas]Nicodem - 20-11-2011 at 13:27
The preparation pretty much depends on which zinc silicate you want. Do you want willemite, hemimorphite, or some other, do you need amorphous or
polycrystalline, etc. You need to specify that or else it is too much work to search the literature for you, because the synthesis procedure is
different for each. Before I even go looking the literature I want to know what to look for. Often, the general procedure for preparing silicates is
to calcinate the metal oxide or carbonate with silicagel, but I do not know which of the several zinc silicates is produced by the calcination of the
stoichiometric ZnO and SiO2 mixture. Some compounds require milling and a second calcination to achieve complete conversion and zinc compounds are
especially troublesome because of the volatility of ZnO which causes disturbances in the correct stoichiometry and thus formation of a second phase or
a different compound. Unless you have a powder-XRD instrument, you will need to follow exactly the published procedure and trust that what you get is
identical to what the authors got.
Exceptionally, some such compounds can be prepared by wet chemistry. For example (from a 5 sec search), zinc silicate was attempted via wet chemistry
and was successfully prepared from 0.00185M aqueous silicic acid, but the result, after a nontrivial procedure, was an amorphous zinc silicate (Clays and Clay Minerals, 22, 409-416).
Your other desire to prepare zinc silicate crystals is even more of trouble. Preparing silicate monocrystals from transition metals is unlikely to be
something easy.
By the way, nice work on the picture. Is that a zinc silicate based glaze? Your work?
[Edited on 20-11-2011 by blogfast25]wyndham - 20-11-2011 at 14:32
Thanks for the responses. Zince crystals gathered from the smokestack of Zinc smelting is what has been used as a seeding crystal by other potters as
well as some Willimite which maybe the same.
The photo's I've seen are of a reddish crystal, very small almost table salt size.
When calcining any material I use ,as well as driving the moisture out of some old zinc oxide, I go to about 1100 deg f. Would this be the correct
temp for the zno and silica gel
I'm open to testing several different methods and if none work, oh well nothing really lost.
The photo I posted is of my work. That piece is a glaze that has 3 % nickle carb for the colorant.
The glaze itself contains
frit 3110 a low alumnia glass frit 52%
calcined zinc oxide 26%
silica 18%
clay 2%
This is fired to 2300 Deg f then down to 2100 deg f and held for 5 hrs. This is the sweet spot for the zinc silicate crystals to grow.
I think that any crystalline material that would come from this test would work as a seed. I would sprinkle a bit of it on a wet glazed pot much like
salting a steak as learn what happens.
The goal is to increase the location and size of the crystals and have a seed supply handy at all times.
Here is a link to a crystalline group I belong to, with some examples of crystals on vases. http://s3.excoboard.com/crystal/64484/861727
Thanks again for what you have shared. Regards WyndhamSedit - 20-11-2011 at 17:41
Wyndham is that your plate in the photos? If so I have seen your work online in the past and I must say I like it.
I have always just used the run off which I'm sure you are use to seeing given the fluidness of the crystal glazes. If you crush the drippings these
can be used as seeds in the next run.blogfast25 - 21-11-2011 at 05:45
When calcining any material I use ,as well as driving the moisture out of some old zinc oxide, I go to about 1100 deg f. Would this be the correct
temp for the zno and silica gel
Probably not as the individual melting points of ZnO and silica are much higher than that.
You indicate firing capability of up to 2300 C, I think 2000 C (several hours) is probably a minimum for synthesising zinc silicate by fusion of ZnO
and silica. But it’s by no means guaranteed you obtain anything like Hemimorphite. Still, it would be my starting point if I had that kind of firing
capability though (green with envy!)… wyndham - 21-11-2011 at 06:56
blogfast25, thanks for the info.
Sedit, I'll try the drips, any links to your work, would like to see some.
WyndhamSedit - 21-11-2011 at 07:20
Na sorry, its just something I dabble in from time to time, chemistry and ceramics have alot in common. I have two kilns but rarely find the time to
use them anymore. I'm mostly a sculpture when I find time but the last three or four projects have been destroyed by my kids before completion and it
kind of puts a damper in everything when you don't have your own space to work. Also watching finished work crash to the floor time and time again is
a bit heart breaking.
I have a couple damaged pieces floating around I could take pictures of but the crystal glazes generally gave me problems due to lack of frit 3110 at
the time meaning I had to low fire(relatively) the glaze first then refire it at the crystal schedule in order for it to look ok.blogfast25 - 21-11-2011 at 09:02
you get my point, but if I have my choice I would not doubt be gilded.