[spring]

I have some decals that I bought and I would like to use them on plates. Before I use them I want to make sure they are food safe.

Also, what about the sepia colored ones that you make yourself?

Thanks in Advance,

Spring

 $(KGrHqQOKpcE3JTCJC14BN6Y6!j0wg~~_12.jpg (35.1K)
Number of downloads: 6

[Chris Campbell]

do you put clear glaze over them?

[spring]

Chris Campbell, on 18 September 2011 - 09:07 AM, said:

do you put clear glaze over them?

These are over glaze decals fired to cone 018, so no I don't. Is there a way I could without killing it?

Thanks
Spring

PS Thanks for the compliment about my profile, that was really sweet of you!

[scoobydoozie]

My experience is that commercial decals are normally food safe. If there is a manufacturer name on the decal or the backing paper, I would recommend double checking with the manufacturer to be certain.

[spring]

scoobydoozie, on 19 September 2011 - 04:22 AM, said:

My experience is that commercial decals are normally food safe. If there is a manufacturer name on the decal or the backing paper, I would recommend double checking with the manufacturer to be certain.

I wish there was but there isn't.

[jo4550]

Hello Spring
I don't know whether this well help you but this is what I know about overglaze decals.

Decals are simply overglaze aka porcelain paint/china paint either screened or printed by computers onto waterslide decal paper and covered with a covercoat.

Overglaze/porcelain paint/china paint is composed of ceramic colour plus flux which determines the firing temperature which in this case is around 800.C (cone 015). So really it is just a very low firing glaze. Traditionally lead has been the source of the flux. Some of the colours contain anything up to 60% flux. Until recently there have been no restrictions placed on use of overglaze colours but now stringent food safe requirements are being put into place as to where the colour can come into contact with food. Colour composition is now changing with the use of boron based fluxes. There is a lot of reformulation happening as high alkaline fluxes change colour responses.

Into this mix then comes the source of the colour. I notice that some of the decals are red and orange/brown. To the best of my knowledge cadmium is involved in theses colours and they will leach in contact with certain foods.

To weigh up your question then I would suggest the following. If the decals are very old stock they would not meet present day food standards. However this should not stop you from using them if you place them where they will not come into contact with food.

Another alternative would be to fire them to a higher temperature to the point where they actually sink into the glaze. They then effectively become inglaze colours. However the rider to that is that you may loose the the red colour as that is very fickle with regards to temperature. Most other colours would not be affected.

Johanna

[spring]

jo4550, on 19 September 2011 - 03:55 PM, said:

Hello Spring
I don't know whether this well help you but this is what I know about overglaze decals.

Decals are simply overglaze aka porcelain paint/china paint either screened or printed by computers onto waterslide decal paper and covered with a covercoat.

Overglaze/porcelain paint/china paint is composed of ceramic colour plus flux which determines the firing temperature which in this case is around 800.C (cone 015). So really it is just a very low firing glaze. Traditionally lead has been the source of the flux. Some of the colours contain anything up to 60% flux. Until recently there have been no restrictions placed on use of overglaze colours but now stringent food safe requirements are being put into place as to where the colour can come into contact with food. Colour composition is now changing with the use of boron based fluxes. There is a lot of reformulation happening as high alkaline fluxes change colour responses.

Into this mix then comes the source of the colour. I notice that some of the decals are red and orange/brown. To the best of my knowledge cadmium is involved in theses colours and they will leach in contact with certain foods.

To weigh up your question then I would suggest the following. If the decals are very old stock they would not meet present day food standards. However this should not stop you from using them if you place them where they will not come into contact with food.

Another alternative would be to fire them to a higher temperature to the point where they actually sink into the glaze. They then effectively become inglaze colours. However the rider to that is that you may loose the the red colour as that is very fickle with regards to temperature. Most other colours would not be affected.

Johanna

Hi Johanna,

Thanks for the reply. I'm about 95% sure these aren't really old. The first time I came across them was a not that long ago and I bought them at a ceramic supply store. They only had a few. When I went back to buy more, they didn't know where they ordered it cuz they didn't remember what I bought. I've also bought about 40 more from a woman who sells them on ebay but she didn't tell me where she got them. As for taking them to a higher temp, that won't work. They are very delicate and when taken just a little higher they burn out.

Also, that's very interesting info you had. Where did you find it? I'm always looking out for technical stuff like that.

Thanks,
Spring

[jo4550]

Hello Spring
A few points here. Just because you have bought decals recently doesn't mean they are recent. Decals are covered with a covercoat and this keeps them intact and safe from harm/abrasion. They wouldn't show their age. In my experience open stock decals can hang around for a very long time.

Second point is this one of safety. I am not saying they are not safe to handle and use. You posed the question of FOOD Safety. I believe that if you are putting the decals in contact with food that it is your responsibility to be sure they are safe. The easiest way to determine this is to fire one as a test and then send the fired article off to a lab to have it tested. There has been a lot of chat going on in Clayart with regard to testing and if you look at their archives you will find recommendations for testing laboratories and their approximate costs.

Your statement that "As for taking them to a higher temp, that won't work. They are very delicate and when taken just a little higher they burn out." indicates to me that they must contain some cadmium and or selenium as on the whole the overglaze colours are very robust and can take a much higher firing. They just sink into the glaze further and become INGLAZE colours as distinct from overglaze and underglaze colours. The lead content doesn't cause them to burn out. They just melt more and settle into the glaze further. The colouring basis of ALL ceramic colours used for under/in/overglaze is the same. It is only the amount and type of flux together with the fineness of grinding that differentiates their use. Cadmium and selinium colours are very temperature specific or otherwise they burn out.

On the other hand if your decals contain lustre and gold you shouldn't be using them for food as they will leach out as well as abrade very quickly.

You asked me where I get my info. I have a very strong interest in using Overglaze in my work for the last 16 years especially in the H&S aspect having undertaken a Churchill Research Fellowship in 2001. Essential scholarly texts are
"Ceramic Colours and Pottery Decoration" Kenneth Shaw;Frederick A. Praeger, Publishers, Library of Congress Catalog card No: 69-17080 and
"Science for Craft Potters and Enamellers"Kenneth Shaw; A.H. & W. Reed Ltd; ISBN 0 589 00739 4
I also get my info from the the UK publications.
COSHH (Control of Substances Hazardous to Health)
CHIP (Chemicals Hazard Information & Packaging for Supply)
Potteries ACOP (Approved Code of Practice)
I also access the websites of Heraeus and Ferro where there is a lot of technical information stashed away in the .pdf's. Online US patent applications also make for interesting reading.

At present I am slowly filling this information into a website I run called overglaze.info. This is a website slanted towards a ceramists/potters understanding of process within overglaze rather than the more narrow viewpoint of chinapainters/porcelain painters. After all it is just another layer in the whole ceramic continuum.

Regards
Johanna