Thursday, October 4, 2012

Back to Backs

Back in June I wrote a couple of posts about bezel setting stones in metal clay, "The First rule of Soldering" and "Romancing the Stone."

Here it is October fourth and I still haven't done my bezel setting.  (Too much golfing, traveling and watching grandchildren .)  But..... today I finally spent some quality time in the studio and got back to it.

Earlier this year, I designed a piece for one of the triangular stones, the Jasper Mookite.  It was a rather expensive stone (so I'm not sure I should have started with it.)

The second thing I shouldn't have done was pick a setting that required so much precision in the placement of the bezel.......... but I did!  Last June I made the backing and eye-balled the size which was just a hair too small once it shrank in the firing process.  (I know that's not the way to get a good fit but I had a moment of lazy insanity.)  

Sooo....... the piece sat for four months until I got the ambition to work on it again.  This time, I scanned the drawing (it was drawn to fit the stone) and increased the size by 115% to allow for the shrinkage of PMC3.  The original piece was three cards thick which was something else I didn't care for, so the new piece is six cards thick.  The extra thickness gives the piece a nice heft to match the weight of the stone and more area to create a nice beveled edge.  

Today I finally sanded the piece, added the hidden bail and beveled the edges in preparation for firing.  I also made two hallmark pieces to add to the back...... 99.9%FS and my AW.  While trying to figure out where to place the two little pieces on the back, I happened to notice the plate with all my paper clay scraps.  In an earlier post this past summer I talked about the work of Vickie Hallmark and how beautiful the back of the pieces were.  She takes as much care with the back as she does with the front of her pieces.

I always tried to make the backs of my pieces clean and neat but I never really designed the back (unless it was for a reversible piece.)  But today I decided to decorate the back with the left-over pieces of paper clay.  

The unfired back.

The piece was fired at 1470 degrees for forty five minutes.  And guess what......... it pretty much shrank to the exact same size as my eye-balled first piece.  Am I good or what?   The thing that isn't good is the fact that my bezel piece barely fits (and I mean barely.)   It's not a whole lot better than it was on the first piece but I think I have it worked out.  

The next step is to join the bezel and the backing piece with oil clay, fire and insert the stone.  I'm getting so close to finishing it (but I've been there before so I'm not holding my breath cause I'll probably pass out.)  


Anonymous said...

I like the design! And the back....

Do you have the PMC "shrinkage ruler" that was in your Rio Rewards toolkit? You could use that to compare your original drawing, your copier-increased template, and your fired piece, to see which transformations came closest to that prediction.

I suggest that because I'm not sure why you used 115% increase, and I also don't know how accurate your copier's increase-feature is. Isn't the rating for PMC3 in the 12 to 15% range for shrinkage? If you were sure it would shrink 12%, then you need to increase it to 114%; if you expected 15% shrinkage, then you'd increase it 118%. (I can give you exact formulas if you want them...) Now, your 115% is in that range, but I've heard of people saying that they always use at least 118%, sometimes even 119!

Go figure....

Alice Walkowski said...

I do have the ruler and I had it out. I was sure I remembered how to use it, but evidently not. It looked the same both ways.

I also had read somewhere else about the 115% increase in size. It was considerably bigger than my template but it seemed to shrink more this time. I expected 12% shrinkage but tried to allow for more.

You are right..... Go figure!

Anonymous said...

Yeah, I wish shrinkage were more predictable. If you bring all the relevant bits and pieces the next time you manage to attend a guild-chapter meeting, I'll be glad to double-check your shrinage and verify how you're using the ruler.