Several weeks ago I sent a kiln pointer on glass separator. (I have included the original message at the end of this email.) Several readers sent in additional pointers that I wanted to share with you:
Paul Bush of Portland, Oregon: “From my experience firing glass for over 5 years in a Paragon GL-24AD, you really need to rewash the shelves every time you fire to a full fuse. It's not worth taking the risk of having the glass stick to the shelf or having the separator stick to the glass.
“I've also found it easy to remove the fired separator with a glass scraper used by painters and found at Home Depot, Lowe’s, or any paint store. The blades are replaceable and really make fast work of this messy job. Some people wet the shelf before scraping to avoid flying particles. Naturally a respirator or at least a HEPA dust mask should always be worn when cleaning shelves.”
Christie A. Wood, Art Glass Ensembles, Denton, Texas: “I've been using kiln wash applied with haik brush on shelves, floor and posts for years. I usually run my kilns up to 500 degrees per hour (melting wine bottles). The kiln wash/separator usually lasts 4-5 firings before needing to be scraped off/sanded down and reapplied. However, some bottles with glass paint embedded in their surface will adhere to the kiln wash immediately, and you have to reapply kiln wash after that firing. But that's what the kiln wash is supposed to do. It's doing its job.”
Charlie Spitzer of Cave Creek, Arizona: “Another, better way to get a smooth surface is to do the multiple coats of wash, then rinse out the brush and use just plain water with the brush for one last coat. Pantyhose work really well, too--lots better than sanding screen.”
Thanks, Paul, Christie, and Charlie for the excellent pointers.
When firing to a “tack fuse” or slightly hotter, I reuse the glass separator several times. (This is the stage of fusing where stringers on the glass surface are still distinct and have not melted flat into the glass.)
Shine a sidelight across the shelf surface or hold the shelf vertically under a light source. With light shining directly across the shelf, it is easier to see cracks and flakes in the glass separator. If you see imperfections, reapply the glass separator. If you have difficulty seeing the surface of the glass separator, play it safe by applying a fresh coat with each firing.
I use a putty knife to scrape off the glass separator. Hold the knife at a 45-degree angle. Removing glass separator creates dust and sometimes flying debris, so you should do this outside. A putty knife will also remove ceramic glaze or glass that has stuck to the shelf. In addition to wearing a dust mask, it is a good idea to wear safety glasses.
Several of you asked about the difference between glass separator and kiln wash. They are finely ground minerals that do not fuse at high temperatures. They serve the same function: to prevent glaze and glass from sticking to the shelf.
The difference between Paragon’s glass separator and kiln wash is that glass separator is ground more finely than kiln wash. Glass separator can also used as a bead release on bead mandrels.
ORIGINAL KILN POINTER A coat of glass separator will usually last several firings. The lower the fusing temperature, the more firings you can get from one application of separator.
If the glass separator is sticking to the glass, fire to a lower temperature. Are you sure you need a “full fuse”? (This is where the surface of the fused piece is completely flat and the separate pieces of glass have merged together.) At lower fusing temperatures, very little glass separator sticks to the glass.
Whenever you notice the separator cracking or chipping on the shelf, apply a fresh coat. Remove most of the old separator from the shelf with grit cloth (available from Paragon). This is an abrasive-coated mesh that allows residue to pass through. Removing the old separator gives you a smooth surface to start with. Then recoat the shelf.
Wishing you an enjoyable July 4th,
Arnold Howard Paragon Industries, L.P. - Better Designed Kilns 2011 South Town East Blvd. Mesquite, TX 75149-1122 Voice: 972-288-7557 & 800-876-4328 / Fax: 972-222-0646 firstname.lastname@example.org / www.paragonweb.com