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 the following for my work.
Steel vs. Ceramic
While some glassblowers still use steel plates, I don't see any benefit, so I use kiln shelves. Steel plates are a ton heavier and for the size of the pickups I do, would be almost impossible to move around. A ceramic kiln shelf washed with Bullseye kiln wash works fine at a fraction of the weight and cost.
A kiln or steel shelf 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, 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 get an even coat of kilnwash and a super-dry 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 is fine but takes a bit longer versus how I do it. And if you don't dry a plate completely, you risk cracking the plate if you've not driven all the moisture out before heating. Unlike fusers, glassblowers usually take a plate very quickly from room temp to fusing temps, so any moisture can easily crack a plate as the water expands quickly. Fusers usually bring plates up much more slowly, which allows any moisture to evaporate out slowly, lowering the risk of cracking the plate.
Here's what I do:
- 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. Then heat any new plate in a kiln to 250 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.
- Once dry, I ramp the plate to about 450 degrees for a half hour or flash it in the glory hole to get it oven-hot.
- 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.
- When your plate is about 400-500 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 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. The reason I wash my plates hot is so I can get a nice coat of kilnwash 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.
- 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 we 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 16 plates I use and it's in good shape.
- If your plate cools down 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.
- The first time you use a newly-washed plate, heat your setup on it in a kiln for an hour just to be double sure it's really dry before transfering to the glory hole.
Ferreti 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. Ferreti should be made from stainless steel rather than regular "mild" steel because stainless doesn't spall with the heat and doesn't rust. I purchase full lengths of 3/8" square stainless stock from a local metal supply and cut it down to the sizes I need.
Here's how I prep ferreti:
- I generally cut the stock into 2' lengths, clean it with a rag and alcohol to get any oil off.
- Sand 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.
- Cut to the lengths you'll use. I find 5 - 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.
- You need to heat them in order for the kiln wash to stick nicely. I find throwing them all in a front-loading kiln or the garage to be 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.
- 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.
- Grab a ferreti with tongs or tweezers and quickly submerge it in the kiln wash. When you pull it out, it should rapidly steam 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 ferreti. Since one dip is usually too thin, I sometimes dip them and toss them back into the kiln to warm back up, then do it again.
Using Shelves and Ferreti
Once you have fully washed and dry plates and ferreti, you're ready to go. You don't have to do anything to maintain the surfaces of the plates or ferreti 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 ferreti 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 sticking and after you pick 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 or done a poor job of washing. 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.