So, you thought you could only powder coat metal? Think again! Powder coating is a great way to give a professional looking finish to metals and also to other surfaces that can safely be baked at 400 degrees for 20 minutes. You may need to finesse the process to get the glass to take the powder, but once you do, it's worth it! In this Instructable, you'll learn how to powder coat a glass jar as a finished piece, or as a surface for laser etching, hand-painting or other techniques. (Check out the Laser Etching Into Powder Coated Glass video here.) Then use them as gifts or in your own kitchen or workshop.
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Step 1: Materials and Preparation
We will not address powder coating technique, but you can find it elsewhere in Instructables, like right here.
Make sure you remember that all materials you use for this project must be safe for baking at 450 degrees. Prepare your piece by removing all gluey lids or stickers, or rubbery gaskets, or anything else that's gooey and not allowed in the powder oven. Then clean it with soapy water, and let it dry thoroughly.
You'll probably want to work with several (3-8?) pieces when you first start because there's a learning curve to the process and it also saves time to work in batches. Further, if you're going to LASER or paint your coated pieces later, you'll need extra pieces for test strips and continued runs. You DON'T need to work only with jars: any kind of glass should work as long as the foil will attract the powder through the glass and you can work with the pieces throughout the process of coating and moving in and out of the oven.
What you'll need:
> Several Glass pieces between 4" and 20" in diameter. (rough estimates. it just has to fit your machines and be movable.)
> Hot soapy water and sponge or rag to clean materials.
> Powder coating materials, supplies, equipment, including powder oven.
> Heat resistant tape- Have about 5-30 feet for a project because you want to use it liberally.
> Aluminum foil. have at least a quarter of a roll to a whole roll for each project just so you don't run out.
> Conductive work-holding device, either hanging or resting, able to be transported to the oven and back.
> Gloves to transport the hot materials
> A clean rack or surface to cool the materials once out of the oven.
> optional: Wrapping paper or something to transport your piece out of the shop after you've coated it.
Step 2: Foil-line and Mask Your Piece.
The powder sticks electrostatically to charged metallic surfaces, so we're going to trick the powder into sticking to the glass by coating the inside of the piece with aluminum foil. Make sure that your surfaces are covered without any holes or gaps larger and about a quarter inch to attain an even coating. Depending on the size and shape of your piece, you may need to use some of the heat-tape to secure your foil.
Once you've finished lining the piece with foil, use the heat-tape to mask the mouth and lips very tightly so no powder sneaks in and ruins your piece. When you're masking the mouth, think about the line you're making with the tape as that is the line the color will follow. If you want to mask the bottom or other areas of your piece, do it now.
Just make sure that the metal on the inside of the jar is connected to the metal on the outside of the jar so your conductivity is not impeded.
Step 3: Set Your Work Holding.
You can choose to hang your piece or set in on a flat subsurface (like a small piece of aluminum or wood) for coating. Remember that you won't be able to touch or adjust a piece that's on the subsurface, so make sure that you can easily rotate the piece and then move it between the powder coating area and the oven using the subsurface.
Also make sure that if you put your piece on a subsurface, you can still reach the piece with the ground on the powder gun to give it the electrical charge it needs. For this job, I used a subsurface, laid the masked and lined pieces onto their mouths, then transferred the whole rig to the oven. You could also hang your piece or figure out another way to get the job done.
Step 4: Apply the Charge to Your Piece.
Once your workholding is set, you can apply the powder gun's ground. If you're working on a metal subsurface to hold your work, you can attach the ground directly to that surface. (I'm showing a top-grounding here, where the ground is connected to the top of the piece. I don't have a photo of the bottom-ground when I applied the ground to the platter.)
Make sure when you apply the ground that you consider how you will rotate the work so that you can cover your whole piece in powder. Once you coat the front half of your piece, you may need to carefully remove the ground, rotate the piece, then reapply the ground. Don't touch or jostle any of your coated surfaces or you'll wreck your powder and need to start over.
Step 5: Coat Your Piece!
Now that you've prepared your glass and applied the charge, you're ready to powder coat! Set up your gun and and oven to the manufacturer's specifications and test your spray. Start your spray off of the piece then pull the stream onto your piece once it's consistent. This will help prevent clumping powder on your glass. Apply a thin, even coat to all of the exposed glass that you can easily reach. Then detach the ground if necessary, and rotate your work to access the un-coated side. Re-apply ground and coat again. Repeat until all sides of your piece are coated with a moderate to liberal amount of powder. Take time to inspect your piece for an even coat and keep applying until you have an even, opaque coating. If your coat is heavier in some spots and lighter in others, light coming through the glass will magnify the difference and your piece might not look as nice.
Step 6: Bake It, Cure It, Unmask It!
Once your piece is evenly coated, you can move it to the oven using either it's hanger or it's subsurface. Make sure to move your piece gently and do not touch any of the powder. If you rub it or jostle it, you might need to remove it all and start over. argh.
Place your piece in the powder coating oven and bake it according the the manufacturer's recommendations for time and temperature. I put my my pieces (on their aluminum holding platters) directly on the floor of the oven and baked for about 18 minutes at 385 degrees.
When time is up, remove the piece carefully from the oven using the platter. You can do a second coating of the same color if you see patches in your first coat. (In this photo, you can see that the powder didn't stick, so I did a second coat). You can also do a clear coat if you want to add protection to your final piece. Once you're done with your final coating, remove the piece carefully using the platter or hanging system you made.
The powder is hard and almost finished, but still needs to cure, so it's still possible to mar your finish if you bump the piece on anything or touch it to dry powder coating powder or greasy surfaces. Put your piece in a clean place to cool for about 45 minutes. Once it's cool, remove the masking. Don't do this while it's hot because you risk damaging your coat and it's also a hassle.
Step 7: Congratulations!
Congrats. You just powder coated glass. If you did a knockout job you got a clean piece without any under-coated spots or leaky powder spots. If you did get spots or inconsistencies, you can do another powder coat. You may have more success with a second coat or cover coat if the piece is baking-temp hot when you give the second coat. Once you've done your final powder coat, you can either leave your piece ike it is, or use it as a canvas for laser etching, painting, screen printing, stamping, or most any other common technique. Now reassemble and set it free. Good work!