Dichro jewelry issue I can't seem to resolve - see pics

[microdichro]

The problem I'm having with making pendants / cabs with dichro is that the dichro layer distorts significantly after firing. The linked photo (stripes) demonstrates what I mean - First I etched the blue dichro with very straight lines that looked great. This was sandwiched between a layer of black and clear (1.6mm). After firing, the lines have visibly bent which shows that the dichro 'pulls'. It is very frustrating because with other detailed etchings, the distortion ruins the image.

Also, the second photo (stripes side) shows the other problem - a jagged layer of dichro is visible on the side of the cab. How do I avoid this.

I have seen beautiful work done on dichro jewelry e.g. Jeremy Bizzano's pendants - no distortion, crips edges and smooth dichro. I just can't seem to achieve this.

Any suggestions?
http://community.webshots.com/user/microdichro

[Kitty]

glass does move when it's hot, so the pattern you put on one layer may shift/bend/stretch. i understand that you are annoyed at not getting the result you intended, but i like the wavy nature of the lines better than if they were straight.

on the second picture, if i understand the pic, you are talking about the dichro coating (blue) leaking out the side. you could put a wider cap on, or you could grind it off and fire-polish. sometimes that leakage around the edge is smooth to the touch, and not unpleasant. sometimes it doesnt feel good, in which case if you hit it with fine-grit water sandpaper, you can knock off the roughness without damaging the appearance -- in my experience. i sometimes lightly "sand" a piece with one of my diamond pads and water -- very lightly, and briefly.

hope this helps a little bit.

[microdichro]

Kitty - I like the lines the way they are too but I did this just to demonstrate the distortion. On other complex etchings, the image looks terrible because it pulls unevenly.

I do grind down the edges if the jagged dichro shows through and then refire it. The problem is that I don't want to refire evey piece I make - that's double trouble.

Thanks for your input.

[Kitty]

oh, i see your point about more complex images. well, you might try firing slower, and/or stopping sooner, when the edges are not yet rounding. i mean, take it to a fire-polish temperature instead of 1450 or 1500. when i make pendants, i usually fire them to about 1500F, and immediately turn off the kiln. try going slower, and stopping sooner. i think that will help.

[microdichro]

That's intersting - what rate do you fire at?

I fire @ 1200F to 1250F and then @700F to 1450- I hold for 10 mins and then switch off.

In total, my total firing time (excluding cooling) is just over 2 hours. How long is your total firing time?

[Sara]

I fire @ 1200F to 1250F and then @700F to 1450- I hold for 10 mins and then switch off.

In total, my total firing time (excluding cooling) is just over 2 hours. How long is your total firing time?

why so hot? why so fast? so many wanna slam dunk and get those pieces out, relax, take your time. many would say I fire way too conservatively for my small pieces, yet I get consistent and predictable results. EXPERIMENT. keep dropping the temp and/or soak times. each color will be different, each kiln is different.

My total firing time excluding cool down about 6 hours. 3 hours to 1000F, soak 20 minutes (If I'm in a hurry only 2 hours, never less), 2 hours to 1250F soak 10 minutes, afap to xxxx soak xxxx, casual natural cool down.


Sara

[microdichro]

Sarah - I bought this jewelry-making video by Vicki Payne and she said that for small jewelry pieces, about and hour and a half is all you need for full fuse. My results, other than the etched dichroic pieces are good. The other consideration is that I need to produce a lot of jewelry every day so time is of the essence.

Having said that, I will experiment with a slower schedule and see what happens.

[Barbara Muth]

Without knowing how you lay up your glass, my educated guess is that you may have a problem with volume control. You are using three pieces of glass, a black, a clear and the dichro. are the black and clear regular thickness, or thin?

You are probably least likely to get distortion if the total thickness, pre-firing is 1/4 inch. If it is less (as in three layers of thin, your edges will pull in and if it is more (as in two layers regular plus one layer thin) your glass will spread out. Either of these movements is likely to distort the pattern of your etching.

As for the dichro scum on the edges, there are tons of posts on that in the archives, both old and new. I agree with Kitty's solution of somehow cleaning it off (sandblast, diamond pad, grinder), cleaning your glass, and firepolishing. If your clear cap is larger than the base and the dichro pieces, you may not get the scum, but you are likely to get new volume control issues.

Good luck solving the problem!

Barbara

[microdichro]

Barbara,

Thank you for your detailed explanation - it definitely helps me understand where I'm going wrong. I do generally use thins in the three layers which explains the problem.

So are you saying that to get the least distortion, either use two regular thickness layers or three regular layers - not thick and thin?

[Tom White]

The idea is to start out with 1/4" (6mm) thickness of glass to avoid movement and distorsion as the glass seeks to get to its natural 1/4" thickness when it is fired. It does not mattter what thicknesses are used in the layers as long as the total thickness is 1/4".

Best wishes,
Tom in Texas

[Tony Smith]

Barbara,

Thank you for your detailed explanation - it definitely helps me understand where I'm going wrong. I do generally use thins in the three layers which explains the problem.

So are you saying that to get the least distortion, either use two regular thickness layers or three regular layers - not thick and thin?

Or like Sara said, fire at a lower temperature (1375 to 1400) and hold longer. You'll get much less distortion.

Experiment more, watch videos less.

Tony

[microdichro]

The idea is to start out with 1/4" (6mm) thickness of glass to avoid movement and distorsion as the glass seeks to get to its natural 1/4" thickness when it is fired. It does not mattter what thicknesses are used in the layers as long as the total thickness is 1/4".

Best wishes,
Tom in Texas

Thanks for the clarification Tom - makes sense. I'll try it out and keep my fingers crossed. Thank you again.

[microdichro]

Tom - thank you too. I will also try firing at lower temperatures for longer. I visited your website and wow - beautiful pieces. Thanks to this board, I have access to artists like yourself - thanks so much.

For jewelry, what is your total firing time?

[Sara]

definitely helps me understand where I'm going wrong. I do generally use thins in the three layers which explains the problem.

So are you saying that to get the least distortion, either use two regular thickness layers or three regular layers - not thick and thin?

au contraire, Michrodichro. quit watching videos and get yo'self experimenting more. Vicky puts out a good video, yet it is only the beginning of an experience and knowledge of glass and good result.

I use 3 pieces of thin for my charm pendants, have no weeping of dichroic on the sides and no distortion of image on the pieces. it's in the control of your firing, and you can "get away" with lots when you learn this and how to manage the glass in your particular kiln.

since you mention needing to produce many pieces a day I'm assuming that your using a quick fire type of kiln, as great as they are it's much more difficult to do a controled burn

Sara

[Sara]

First I etched the blue dichro with very straight lines that looked great. This was sandwiched between a layer of black and clear (1.6mm). After firing, the lines have visibly bent which shows that the dichro 'pulls'. It is very frustrating because with other detailed etchings, the distortion ruins the image.

Micro, I'm looking at your piece again and think that some of the distortion is simple physics. you've got the image to the edge of the glass . . . which naturally curves down and around. I believe you might want also to experiment with adjusting your image within the frame of the glass.

S.

[microdichro]

Sara - I will try to hold at 1420F for 20mins rather than 1450 for 10mins and see what happens. I use a Skutt GM10F kiln with controller.

As for placing the etched image more centrally, i tried that with better results but I do want to have designs which start from the edge - besides, this has become somewhat of a challenge!

Thanks for your input - and my compliments on beautiful work.


[/quote]

[Sara]

Sara - I will try to hold at 1420F for 20mins rather than 1450 for 10mins and see what happens. I use a Skutt GM10F kiln with controller.

As for placing the etched image more centrally, i tried that with better results but I do want to have designs which start from the edge - besides, this has become somewhat of a challenge!

Challenges are fun! good luck and share your successes.

For your hold pattern, try less time to begin with and increase hold as needed, 20 minutes sounds very long. Remember that the dichroic is simply a coating on the glass and 'floats' or wants to move as the glass does. This can be used to advantage too. We have different soak times for each color or result we do. If i were to fire the example you show I'd start in my JenKen at 1428F for 8 minutes and adjust from there. . . 1 or 2 minutes makes a huge difference in results also. if it wasn't enough for the look I wanted I'd go up ONLY 2 degrees and not change the soak time OR add 1 or 2 minutes to the soak and not change the temperature.

Figuring out what works for each kiln is an exercise in patience and a fabulous way to learn glass and your kiln. I've pounds of misfired pendants from over the years to prove it too

thank you for your gracious compliments,

Sara

(and thanks for noticing no 'h' )