fusing sterling silver with art clay

[dubmblond]

Hello All
I was searching for an answer about art clay (slow dry) and sterling. I couldn’t find my answer in the archive.

I'm making a replica ring for my sister of my grandmothers ring (1930's or so). The center is the replica bit that I've copied in art clay. The band will join on either side of the center piece. I would like to join the band to the center piece while I’m firing (torch). I don't want to embed the band (it would "change" the replica) I got a few questions so her they come:

1   I’m I correct in thinking that the sterling does not really fuse together with the clay (like solder would) due to the oxidation that the sterling gives of?
2   I’m I right that the join sterling / clay must always be embedded in the clay and that the shrink is the main hold?
3  If I can join it while firing I was wondering if I need to flux the sterling or not.
4   What will be stronger? A soldered joint or... fired in one go?

by the way I don't have paste or other things only 650 and 650 slow dry (If i need paste I make it myself by watering down the 650)

Thanks for any input

Arts and Crafts by Monique UniqueDubmblond

[Metalman]

First - if posssible, use fine silver for this. 2nd best would be to use the Argentium® Sterling. This will eliminate the oxidation and firescale problems.
If you have to use sterling, the best scenerio would be to build your art clay and then solder it to the sterling after firing using traditional metalsmithing methods.
this works well the only consideration is that the Art Clay soaks up more solder then milled silver

1   I’m I correct in thinking that the sterling does not really fuse together with the clay (like solder would) due to the oxidation that the sterling gives of?
  This is basically true but I have had good results joining sterling jump rings or wire into the ACS materials. I sand or pumice clean the sterling first, then give it a wipe down with solvent alcohol. If it is really clean , I can get 2 or 3 layers of thinned paste to stay on the surface of the sterling. If the sterling is completely enclosed by a layer of Art Clay paste, it seems to not oxidize or firescale and does seem to bond well.
2   I’m I right that the join sterling / clay must always be embedded in the clay and that the shrink is the main hold?
When I build in wire or other elements, I usually try to have a mechanical connection as wellas expecting some bonding. I probably err to the side of excess here but I like to have solid pieces. Shrink is a factor here and does help hold but it more frequently cause some cracking around the various elements being included. This cracking is easliy filled with paste or clay and refired. It is best not to do any finish work until all of you refiring is done
3  If I can join it while firing I was wondering if I need to flux the sterling or not.
I have not tried using flux in these circumstances - might work, but I think the time length of the firing would just burn off the flux - this is an experiment that needs doing and reporting on
4   What will be stronger? A soldered joint or... fired in one go?
depends on the materials and the strength of the build in. Hard soldering is a very strong way to join metals [as opposed to soft soldering]

by the way I don't have paste or other things only 650 and 650 slow dry (If i need paste I make it myself by watering down the 650)
this is a fine way to have paste when you need it

Another way to join fired Art Clay to metal or other fired Art Clay is to use Oil Paste - this Art Clay product works well joining pin stems, bezels and broken fired ACS pieces. This would be one way to go with the project6 outlined above. Odinarily kiln fired, you can torch fire Oil Paste but must be sure it is completely dry before you fire. You may also want to hold it at temp with the torch a little longer then regular firings

[dubmblond]

Hello Metalman

Sorry for my late thank you, my pc was giving me some trouble.
I did finish the project and chose to solder the piece on afterwards.  I wasn’t in the position to start the project again if it failed (time deadline) so I chose the safe option rather than experiment. I will experiment and let you know my findings after I’ve done it.

I was wondering what you meant by the soft and hard soldering.
Am I correct in thinking that you mean by:
Soft soldering: all solder containing a mixture of Pewter and Lead. Here for using a soldering iron at low temperatures.
Hard soldering: all Sterling Silver solder. Hard, medium or soft solder would all be called hard soldering for it’s been done with a flame and a higher temperature.  

Or do you mean that there is this difference within the Sterling Silver solder range. Using hard or soft Sterling Solder?

Thanks again for your help
Dubmblond
http://home.planet.nl/~grego079

[Metalman]

No, you have it right there!!
Hard Soldering [more properly called silver brazing] is higher temp and requires pickling. This would also refer to Gold solding. [again a brazing technique]
Soft Solder is lower temp and usually contains Tin, Zinc, Lead and other metals. Stained glass solders contain 40% to 60% lead.  The soft metal solders should not be used if the metal piece they are used in will ever be heated to Hard soldering temperatures.
R&T carries StayBrite solder which is an alloy of Tin and a small % Silver.
Pewter is an alloy alloy of metals that can contain various percentages of tin, lead, antimony, bismuth, copper or silver. These days, most pewter does not contain lead butthis is an ongoing concern, especially with low grade pewter mixes. The higher quality pewters are at least 92% tin and contain no lead at all.

[dubmblond]

Follow up on this project.

The finished ring "lived" about 4 days of wearing. Then the soldering broke of the artclay center piece '>
Back to the drawing board I guess

Dubmblondmonique unique

[Metalman]

Checking details here.
You soldered the pieces together - I am guessing with soft solder and after a couple of days it came apart.
I suspect, if the above is true that the smaller piece you were attaching got hot enough to melt the solder  and bond; but the larger piece was still too cool for the solder to properly flow and make a stronger join.

The reason the pieces stayed together for a while is because the solder flowed enough to get into the crevices of the 2 pieces and hold them together mechanically without a proper bonding - this is also why it came apart - it was stuck but not bonded

If you used the higher temperature solder - basically the problems and reasoning above would be the same.

There are 2 vital aspects to soldering [soft or hard] 1] proper melt or flow temperature 2] Cleanliness of the metal to be joined - flux is a factor here.