Back to Ganoksin | FAQ | Contact

Trouble shooting LCE-3 powder


#1

Every time I use LCE-3 (white) as a counter enamel on copper OR
silver, it turns a pale green around the edges or on any internal
area that is only thinly covered with LCE-3. I am assuming this is
oxidation. But why and where from? The LCE-1 (black) does not show
this anomaly (naturally).

Here is what I do:

  • If I am using silver, I deplete it first

  • I use Cratex wheels to smooth the copper edges, but have NOT used
    the Cratex on silver during this experiment

-The metal pieces are thoroughly cleaned with PennyBrite, glass
brush

  • I mix the LCE powder with distilled h20 in a clean container
    stirring with a clean plastic spoon.

  • I believe that I am following proper enameling procedures (i.e.,
    avoiding cross contamination, using clean tools, clean paper, keeping
    my area tidy, so on…)

  • I paint the LCE-3 mixture on the back thickly and allow to dry
    completely on top of my kiln

  • I sprinkle enamel the front

  • fire at 1450 - 1500 for 2.5 minutes

  • my Pickle is Citrex - which does nothing to remove the green stain

  • however, I can grind it away with alundum stones

  • my kiln is an ArrowSpring AF99 t4 with a kiln washed ceramic floor
    board

  • my trivets are from Thompson enamels as are the mesh screens

  • I have successfully enameled both silver (depleted or not) and
    copper previously and have not run into this type of problem

Now, I can only assume that:

  1. My brushes might be contaminating the LCE-3, but wouldn’t the
    entire surface be affected?

  2. Even though I regularly clean my trivets, they might be
    contaminating the edges

  3. Or, ???

I seriously enjoy this site and the discussions; I always enjoy
visiting the sites of contributors and am in awe of the amount of
skill, creativity and knowledge presented here.

Thank you all so much for everything

Sandra Gilbert
Snohomish, Washington


#2

Sandra,

When your enamel is thinly applied (often on the edges) and then
fired too long or too hot, copper oxides (green) will be taken into
the liquid glass.

This is a well known problem with transparent enamels, but I imagine
it could happen with LCE-3 too.

I currently only torch-enamel, so it’s easy to see when to pull the
torch off the metal/enamel. However, when I kiln-fired, I always kept
the kiln at 1450F and most jewelry-sized pieces only needed 2 minutes
(all Thompson enamels, which includes LCE-3). So, you may want to add
a little more enamel, back off the heat by 50F and shorten your time
by 30 seconds (or cross your fingers and pray, which seems to be the
only solution on many enameling problems :wink:

Good Luck,
Jamie


#3

Every time I use LCE-3 (white) as a counter enamel on copper OR
silver, it turns a pale green around the edges

It’s a normal reaction. Something in the white is reacting with the
base around the edges because when the enamel fuses, it pulls back a
bit and that remaining on the edges is thin. Flux will often react on
copper this way as well. The only cure for the white is in your final
firing to paint a frame around that greenish area with more white.
You have to keep the covering thin enough to whiten the edge but not
too much or you will get bumps if you are firing upside down. I
always liked the framing effect of the green edge but if you want a
perfectly white back or front, then you need to put on another coat
to cover the green.

Donna in VA


#4

The white is turning green because the coat is too thin. Edges tend
to burn out, because they are edges. Perhaps a second coat making
sure that the edges are more thickly covered than the internal body.

Kay Allen


#5

You may be getting solution of copper into the enamel, dont know
about LCE-3 but most of the european enamels contain a lot of borate
flux instead of lead oxide to lower the liquidus point on this will
dissolve any oxide present. The porosity of the enamel in the
thinner spots will accentuate this. To prevent this a fluxing enamel
can be used as a base coat. This is clear but can alter the colours
of other transparent enamels applied to it. Another possibility is
that you are geting a bit of diffusion of the copper, try less time
in the kiln or multiple firings to avoid orange peel of the surface.

Nick Royall


#6

I want to thank everyone who responded to my query. We had a family
emergency that has kept me busy and I am just now getting back to
’normal’.

From the replies, it does not seem that I have a contamination issue
in my shop - which was my worst fear. (Well, one of them anyway ;-0
) I have done torch firing and LCE as a counter enamel doesn’t seem
to like direct heat.

I had my kiln temp up because the temp would drop to as low as 1350F
when I inserted the enamel pieces (I have a bead door and work pretty
quickly getting the enamel pieces in and out). In retrospect that was
dumb. I will adjust the temp, shorten the firing time and use a
thicker coat of counter enamel. Or just stone the edges and
reapply/fire.

Thank you Donna for pointing out that the green edge is a normal
reaction and Kay for suggesting that the coat was too thin.

Nick wrote:

most of the european enamels contain a lot of borate flux instead
of lead oxide to lower the liquidus point on this will dissolve
any oxide present. The porosity of the enamel in the thinner spots
will accentuate this. 

-Very interesting comment, I will look into this further. I
currently use lead-free Thompson enamels.

And Jamie summed it all up:

However, when I kiln-fired, I always kept the kiln at 1450F and
most jewelry-sized pieces only needed 2 minutes (all Thompson
enamels, which includes LCE-3). So, you may want to add a little
more enamel, back off the heat by 50F and shorten your time by 30
seconds (or cross your fingers and pray, which seems to be the only
solution on many enameling problems ;-)

(I hope I didn’t miss any replies.)

Again, thanks to everyone - And, I hope everyone has a very happy,
safe and delicious Thanksgiving.

Sandra Gilbert
Snohomish, WA


#7

Sandra,

I have done torch firing and LCE as a counter enamel doesn't seem
to like direct heat. 

Something that is rarely mentioned in instructional material that
I’ve read (maybe it’s common sense, but not to me) is that many
enamels don’t like to be hit directly with a torch until they have
started to melt. So whether it’s LCE, transparent or solid enamel, I
always either (a) enamel one side at a time, or (b) when I need to
enamel both sides at once, I use a reflective heat from the torch
until it gets toward the orange peel stage. Then I can put the flame
directly on the enamel and it finishes up just fine.

Jamie


#8

Thanks Jamie;

And you are right - no manuals seem to explore or discuss using
direct heat. I figured it was trial and error since it seems to work
with some opaqaues - I hadn’t gotten to the point of trying reflected
heat until the enamel reached the orange peel stage. Thanks a bunch
for that tip.

I do like using the kiln for dual-sided enameling - warms up my cold
garage shop :slight_smile:

Sandra Gilbert
Snohomish WA