How I Prep a Plate for Cane and Murrine

How I Prep a Plate for Cane and Murrine

Getting cane and murrine onto a blowpipe presents a number of challenges, the first of which is what kind of plate to use and how to prepare it.  I've tried all different methods and settled on what describe below.  You've got to be careful about prepping and using plates or you'll get the dreaded sticking, but once you get it dialed in you'll rarely run into this problem again--until the plate needs re-washing.

Steel vs. Ceramic

While some glassblowers still use steel plates, they're heavy and I don't see any meaningful benefit, so I use ceramic kiln shelves.  For really large pickups, steel would be almost impossible to move around.  A ceramic kiln shelf washed with Bullseye kiln wash works fine at a fraction of the weight.  

Washing Plates

All shelves needs a non-stick coating or hot glass will quickly stick to it. There are a couple options for washing plates and I've heard some serious voodoo about the process, (most surpisingly from a teacher at Pilchuck) but I don't think it has to be complicated at all. I use Bullseye Kiln Wash, but if you have a great source for mud from the lagoon near Murano, or some kind of clay face mask, or love graphite spray, have at it (that's some of the voodoo and I have no idea if it works). The goal for coating plates and ferreti is to apply an even coat of kilnwash and super-dry the plate before you try to use it.  You can wash your plates just like fusers do with a brush, doing multiple coats in each direction, then dry it out slowly in a kiln before using it.  Doing it this way works great but takes longer versus my approach.  And if you don't dry a plate completely, you risk cracking it.  Unlike fusers, glassblowers usually take a plate very quickly from room temp to fusing temps, so any moisture can crack a plate as the water expands quickly.  Fusers bring plates up much more slowly, which allows any moisture to evaporate out slowly, lowering the risk of cracking the plate.  

I wash my plates while hot so I can get a nice coat of kilnwash on it without getting the plate wet since all the water boils off as soon as the wash is applied.  This means I don't have to dry my plates after washing them.  Here's how I wash plates hot:

  1. Wipe down new plates with a most sponge to remove any dirt or dust.  If the plate feels especially rough, you can give it light sanding to smooth it out.  If it needs to be cut, do it now.  Then heat any new plate in a kiln to 220 degrees for a couple hours to get it nice and dry.  If you're washing a plate you know to be dry (because you've used it before, live in Arizona, etc) you can skip this.  
  2. Once dry, I ramp the plate to about 500 degrees for a half hour or flash it in the glory hole to get it oven-hot.  
  3. While its heating up I mix up or re-stir my Bullseye Kiln Wash.  Don't skimp on the stuff--use the recommended ratio or a bit more, but you've got to really stir it well to keep it all in suspension just before you wash.  
  4. When your plate is about 500 degrees throughout you're ready to wash.  A good method to know if its the right temp to wash is if you drip some water on the center of the plate and the water boils off rapidly.  If the water doesn't wet the plate and just rolls off, the plate is too hot (the water droplet rolling around is the Liedenfrost Effect).  If the water wets the plate and doesn't steam off quickly, its too cool.  Test the center of the plate since that will usually be the coolest part of the plate.  
  5. When the plate is the right temperature I usually do 4-6 coats starting in different directions with a 3-4" wide paint brush with natural bristles.  If you use synthetic bristles, they may melt while washing the plate, contaminating the coating.  The natural bristles can scortch a bit if you're too slow or don't wet the brush enough, but it's minimal and doesn't effect the coating.  I've been using the same brush for probably eight years to wash the 20+ plates I use and it's in fine shape.  
  6. If your plate cools down too much while you're washing and gets a little wet, no big deal--just flash it in the GH or put it back in the kiln for a bit to dry it.  As long as you get it hot again quickly, the water in the plate isn't likely going to saturate it so it should dry out in the glory or kiln without cracking.  
  7. After you're done washing plates, I leave them in the 500F kiln for a few minutes just to be sure they're dry.
  8. The first time you use a newly-washed plate, heat your glass on the plate in a kiln for an hour just to be double sure it's really dry before transfering to the glory hole.

If your plate cracks or breaks after you use it, it either already had a crack and the heat cycle and jostling from forking it around made it separate or you didn't get it totally dry before heating it in the gh.  

Prepping Ferretti

Ferretti have two important uses--to keep your cane from rolling off the plate prior to fusing and to shield the edges of the pickup from the flame.  Many people either don't understand the latter purpose or underestimate its importance.  Ferretti should be made from stainless steel rather than regular "mild" steel because stainless doesn't spall with the heat (often flipping little pieces of metal flake onto your glass) and doesn't rust.  Stainless does shed metal dust from the heat, but usually happens after cooling and it's only a problem if you overheat your ferretti. I purchase lengths of .4375" square stainless stock from a local metal supply and cut them down to the sizes I need.

I wash ferretti hot as well since it's really quick and easy to do.  Here's my process:

  1. I generally cut the 12' stock into 2' lengths, then clean each with a rag and alcohol to get any oily dirt off.
  2. If they're still a bit dirty I sand and all surfaces on a belt sander. It's easier to do at this size versus after they're cut to short lengths and your fingers have a higher risk of being sanded.  Depending on how much crud is on them and the condition of the belts I use 80 to 120 grit.
  3. After they're clean, cut to the lengths you'll use.  I find 6" lengths to be most flexible.  Turn the edges where you cut them against the belt sander to smooth out any roughness from the cutting.
  4. You need to heat them in order for the kiln wash to stick nicely.  I find throwing them all in a front-loading kiln at 900F or the garage is the easiest way to get them hot but also get them out.  Let them sit in a kiln until they're fully heated--20 minutes is probably plenty.
  5. While they're heating prepare your kiln wash.  Just before you're ready to wash make sure you give the wash solution a good stir.
  6. Grab a ferretti with tongs or the pipe grabber on some diamond shears you don't love and quickly submerge the enire ferretti it in the kiln wash.  When you pull it out, it should rapidly boil off the water, leaving a dry thin layer of kiln wash.  If they're the right heat and you're quick, sometimes you can get two dips on them before they cool down too much for this process to work.  Do this with all your ferretti.  Since one dip is sometimes too thin, I sometimes dip them and toss them back into the kiln to warm back up, then do it again.  Be sure the stir your kiln wash every couple ferretti.

Using Shelves and Ferretti

Once you have fully washed and dry plates and ferretti, you're ready to go.  You don't have to do anything to maintain the surfaces of the plates or ferretti but do be careful with the surface and your heats.  Depending on your frequency of use, a washing should last for months as long as you don't overheat your plates, scrape them with a tool or get them wet.  Washed ferretti lose their non-stick properties if they get dropped into wax on the floor, get wet or fall off into the glory hole (get them out asap!).  If you're careful about heating you won't have any glass sticking issues and after you roll up you can use a small handheld brush or moist cotton rag to quickly wipe off any dust. If your glass sticks you've either gotten it too hot, done a poor job of washing or it's time to re-wash your plate. And if you overheat your glass, you'll also burn up the kiln wash more rapidly which will require you to re-wash more frequently.  

For most simple cane thats pulled hot, even and about pencil thickness or thinner, you don't need to preheat the cane or plate--you can load the cane on the plate and go right into the glory hole.  If your cane is thick, irregular or stressed (like from twisting) I preheat the cane setup on the plate in a kiln or garage for 20 min before transfering to the GH.  Cane that can't even handle being preheated in a kiln and crack just going to 900 is usually irregular in shape, super thick (and should have been annealed), inconsistent or has incompatible color.  
To heat cane or murrine, plan on multiple heats, starting with a longer first heat, then shorter and shorter heats as it warms up.  The first heat should soften the glass enough to tack fuse.  Depending on your GH's burner configuration you might want to flip the plate between heats.  Don't let a plate sit in the hole and puddle your glass--the edges will flow and stick and then you're totally screwed no matter how much kiln wash you use.  I go for a dark orange glow in the glass, squeezing it at each heat as it gets hotter.  After your cane or murrine is initially fused together, move the ferreti an 1/8" away from the glass so you don't have any risk of sticking.  For larger or longer pickups I also torch the cooler parts of the glass (usually the back and/or center of the plate) in between heats to even out the temps.  Each subsequent heat get it incrementally hotter until you've squeezed it all together, the heats are even and it's ready to roll up.  Be sure to never try to squeeze cool cane or murrine--you'll end up with a hot mess.
I probably wash some of my shelves about once every 6 months, but I've got around 20 shelves in rotation.  I'd estimate I get about 20 uses out of a shelf before it needs to be re-washed. I re-wash plates and ferreti when I begin to get stickiness or crap on my glass after a pickup.  (I keep a dremel handy for the times I pick up some crap from the plate or marver).  Don't be shy with the wash and don't overheat and your prepping will last a good long time.
Hope this helps!