jgourlay
Hazard to Others
Posts: 249
Registered: 9-7-2008
Member Is Offline
Mood: No Mood
|
|
Talk to me about V2O5 and toxicity in general
Gents,
Lately I've become interested in making my own pottery glazes. This pursuit comes thick and heavy with MSDS sheet and toxicity warnings. The base,
literally and figuratively, of most of these warnings revolves extensively around "white" and "red" lead because white or red leads form the
high-percentage content "base" for about 75% of all pottery glaze recipes.
However, many recipes use a few percent of Vanadium Pentoxide. Now, I've read the MSDS on V2O5 and it looks only slightly less hazardous than a
straight chlorine enema. However, the books are not nearly as wound up about V2O5 as they are, say, copper carbonate and chromium compounds. Copper
carbonate, btw, is that pretty green string of malachite beads your wife is wearing out to dinner tonight.
Interestingly, there are several commercial glazes that use V2O5. I say "interesting" because the glazes generally come in three classes. 1. "Safe"
full stop. 2. "harmful if ingested, safe for food use after firing", and 3. "harmful if ingested, not safe for food use after firing". Most of the
recipes containing V2O5 are in the "Safe" category. Now, the warnings indicate you take "safe" with a grain of salt in that 1) they are only safe in
liquid, not powdered form and 2) you shouldn't be drinking them. What they mean by "safe" is that your kids can paint with them under supervision and
that you don't need to wear gloves or a respirator while using. Additionally, in the recipe books, the recipes listed as "toxic" that use V2O5 are
only listed as toxic if they also contain a lead, barium, or if I remember correctly a high percentage strontium compound.
So.....what's the deal with V2O5? Is it dangerous but less dangerous than Copper Carbonate? Is it considered less hazardous by potters because it is
less frequently used and in much smaller doses than most other compounds? Ditto questions for the same reasons on Uranium Oxide and praesodymium
oxide and the other rare-earth oxides.
Also, anyone know of a good source for V2O5 in sub kilogram quantities?
|
|
|
per.y.ohlin
Harmless
Posts: 27
Registered: 14-11-2009
Member Is Offline
Mood: No Mood
|
|
The different amounts of compounds likely has a significant effect. If two compounds have a similar toxicity, but one is present in much larger
quantities, the compound present in larger quantities will obviously be the one to worry about. Routes of absorption can have an effect as well.
Silica is a significant inhalation hazard in a dust form, but it is completely nonhazardous via ingestion or skin absorption. Vanadium pentoxide might
be overall about as hazardous as copper carbonate, but in a powder form copper carbonate may be more hazardous.
As for a source, seattle pottery supply seems reasonable. United Nuclear has a similar unit price for less material, but IIRC the shipping costs are horrible.
|
|
|
jgourlay
Hazard to Others
Posts: 249
Registered: 9-7-2008
Member Is Offline
Mood: No Mood
|
|
Thanks!
|
|
|
Jor
National Hazard
Posts: 950
Registered: 21-11-2007
Member Is Offline
Mood: No Mood
|
|
I think it is quite nasty stuff:
http://www.jtbaker.com/msds/englishhtml/v2220.htm
http://msds.chem.ox.ac.uk/VA/vanadium_pentoxide.html
|
|
|
jgourlay
Hazard to Others
Posts: 249
Registered: 9-7-2008
Member Is Offline
Mood: No Mood
|
|
Thanks for the MSDS. That MSDS is better than the one I printed out the other day.
I've seen several cases like this. HORRIBLY toxic stuff...and yet people seem to have used it pretty successfully over the years without falling over
dead.
Not minimizing the hazard...just trying to get a better perspective.
|
|
|
ScienceSquirrel
International Hazard
Posts: 1863
Registered: 18-6-2008
Location: Brittany
Member Is Offline
Mood: Dogs are pets but cats are little furry humans with four feet and self determination! 
|
|
Realistically if you are using vanadium pentoxide on a micro scale then there should not be a problem as long as you have reasonable containment and
gloves etc.
Compared with dimethyl mercury it is not that toxic!
Lead is the major heavy metal in pottery glazes and it is accumulative.
|
|
|
Sedit
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
Ok I cant help you with the vanadium pentoxide sorry but I can help you avoid the worse ones out there. Lead oxides are primarly used as a red
coloring agent and work very nicely producing a bright colorful red with ease although food safe is out of the question because of acidic foods can
leach the lead out. There are some uses as a flux of the lead oxides IIRC but there are many other options there.
Lead as a coloring agent can be done away with using Cadium and most red glazes anymore do just this but Cadium isn't nothing to turn your back on
either. There is a safer no toxic although expensive alternative which is Au and its oxides and salts for bright reds and personaly I find this
produces the best results of all of them creating a bright but transparent red. Iron can produce earth tone reds but I feel these suck for most
applications as you must recrystalize the iron oxides out in order to produce the red color.
If you need any help for glazes I have have taken classes a while back and if needed I could call on much experties help with no problem just PM me
and let me know.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
JohnWW
International Hazard
Posts: 2849
Registered: 27-7-2004
Location: New Zealand
Member Is Offline
Mood: No Mood
|
|
There are Fe(III) compounds that can be used as red paint pigments, as in "ferric red" roof paint.
|
|
|
Sedit
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
As I stated but these SUCK for red pigments in glazes because the oxides must crystalize out of the melt in microscopic crystals.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
The problem with V2O5 in potteries applications is that it is somewhat volatile, certainly when temperatures are applied, such as common in making of
ceramics. So, exposure to V2O5 is quite easy and that is why it is regarded a higher risk chemical in pottery applications.
If you plan to use V2O5 for its intended purpose then you really have to take into account the possibility of vapors of this compound, which will form
ultrafine breathable dust when it condenses to a solid again in colder air.
I sometimes use V2O5 for experiments in aqueous solution and in that application I do not think it is really dangerous.
|
|
|
jgourlay
Hazard to Others
Posts: 249
Registered: 9-7-2008
Member Is Offline
Mood: No Mood
|
|
Woelen, thank you so much for that warning! I have V2O5 on order, and was going to use it until your note. I think I won't use it now. I'm
typically not in the shed when I'm firing, but if it will do as you say then I'm going to reconsider. Especially since my little ones are always in
the shed, I'm very sensitive to hazards beyond what I can reasonably control.
Maybe in the future if I get one of those fan assemblies that sucks fresh air in from the lid and spits hot air through a fan and out the wall I'll
reconsider. But ultrafine condensate all over this small enclosed area isn't going to cut it.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by jgourlay  | | Maybe in the future if I get one of those fan assemblies that sucks fresh air in from the lid and spits hot air through a fan and out the wall I'll
reconsider. But ultrafine condensate all over this small enclosed area isn't going to cut it. |
Take a look
at the Orton Ventmaster. The PDF manual on that page has enough information to make your own.
|
|
|
jgourlay
Hazard to Others
Posts: 249
Registered: 9-7-2008
Member Is Offline
Mood: No Mood
|
|
Man, you guys are such a huge fount of knowledge! Thanks Watson!
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
