Two things you should know about me: I love math and I love words. If I find them together in a math pun like “Pi plate”…well, just imagine me clapping in glee. So, in honour of Super Pi Day this year, where the year took Pi to an extra two digits— 3.1415 instead of the usual 3.14—I transformed all my pie plates into Pi plates by etching Pi on the bottom with a stencil I created in Silhouette Studio (download the free cut file below).
The whimsical math nerd in me was delighted with the pun. And for a first glass etching project, the etching turned out fabulously—I thought it would take a few tries to get this quality! I love the reaction when I give these as gifts (filled with pie, of course, for the recipient to discover the numbers as the pie is eaten :^), and my whimsical math nerd friends—of which I apparently have many—have been parading their glass pie plates through my house for me to turn into Pi plates for them. What a hoot.
The file contains two stencils: one for a regular 9″ or 9.5″ pie plate, and the other for a little mini 6″ pie plate.
What you need…
- 9-9½” Glass pie plate or simpler less expensive pie plates like these, or 6″ pie plates
- Armour Etch etching cream
- Small foam brush
- Vinyl – to use as a stencil. Any temporary or permanent vinyl such as Oracal 631 or 651 will work, I used Con-Tact paper because I didn’t want to sacrifice any of my 631 or 651.
- Transfer tape – to transfer the vinyl stencil to the pie plate. I used clear Con-Tact paper because that’s what I had on hand.
- Squeegee – I like the blue 3m squeegee (it’s large and flexible)
- Isopropyl alcohol (rubbing alcohol) – a few drops
- Facial tissue to use with the alcohol – a few
- Small craft knife – an old paring knife will work well
- Rubber gloves
- Silhouette machine – to cut stencil
- Sink with running water – plastic or stainless steel, NOT porcelain!
What to use as the stencil material?
Some folks use stencil vinyl, others recommend Oracal 631. Yet others swear by adhesive Con-Tact paper, but some say it’s too thin. Certainly, dedicated stencil vinyl and Oracal vinyl are premium products for glass etching. You can’t go wrong there. But they both come with a premium price, and if you’re doing a number of 9″ Pi plates with a 12″ square of stencil material each, you’ll motor through a good volume of stencil material in no time.
I didn’t have any stencil vinyl, and I didn’t want to sacrifice any of my Oracal vinyl colours—how do you choose!? I happened to have some inexpensive adhesive Con-Tact vinyl (typical shelf liner stuff) on hand, so I decided to try that first. It turned out I had two types: clear and white. The clear was super thin. It curled and folded in on itself and proved difficult to work with because it was so flimsy. But the white was considerably more substantial, a weight I thought would work well for stencil material (and—spoiler alert—it does!). I now see why some folks are adamant that Con-Tact paper is too thin for stencil material while others use it all the time—I’m betting the two groups aren’t using the same type of Con-Tact paper.
I wish I could give you different product names for these two types so you could always buy the heavier one, but I no longer have the original packaging and nothing printed on the backing gives any indication of what makes them different, so no help there. However, I did order a package of what Con-Tact calls “Clear Cover” HERE, and something similar in black HERE, and they both turned out to be the more substantial weight suitable for stencil material.
As far as color goes, if I have a choice, I prefer a solid color vinyl over clear when stenciling glass. It’s much easier to see the design against the glass.
The stencil is applied to the bottom of the pie plate on the non-food side of the glass—in other words, upside down—so before cutting, remember to mirror the image (click the ‘Open the Replicate Window’ then ‘Mirror Left’) so the etched numbers end up the right way.
In the Cut Settings window in the upper right tool bar, I used: Cut Mode: Standard, Cut Style: Cut, Material Type: Vinyl, Blade: 2, Speed 3 (I get into less trouble when I slow things down), Thickness: 4 (low number = less likelihood of the blade catching on corners), and Double Cut box checked.
From cut stencil to glass etching…
STEP ONE: Cut the stencil and leave it on the mat while you weed it.STEP TWO: Apply transfer tape to the stencil. Although the extra-thin clear Con-Tact paper is too thin to use as the stencil, it makes an excellent (and cheap!) transfer tape for this project. Start in one corner and smooth down the transfer tape with a slow back-and-forth motion with one hand (the shadow hand below (my other hand was busy snapping pics)) as you slowly allow more transfer tape to be applied with the other. Avoid wrinkles and bubbles as much as possible.STEP THREE: Rub the transfer tape/vinyl/backing sandwich all over using firm pressure to make sure the transfer tape is well stuck to the vinyl. Pay special attention to the “floaty” pieces—or ‘counters’ as the typography folks call them—inside the fours, sixes, eights, and nines.
STEP FOUR: Carefully peel the transfer tape from the backing. The vinyl should come away from the backing and stick to the transfer tape. If some vinyl persists in sticking to the backing, stop, smooth the transfer tape back onto the area, give it another rub, and lift the transfer tape again. Once removed, place the stencil on a work surface, transfer tape down, sticky vinyl side up.STEP FIVE: Clean the bottom of the pie plate with ispropyl alcohol to remove any finger oils. The smallest amount of oil on the glass, even if invisible to the naked eye, could prevent the etching cream from reacting properly with the glass.
STEP SIX: Positioning a stencil where you want it is usually very challenging, but because the pie plate is transparent, it’s easy peasy on this project. Simply hold the rim of the pie plate with both hands, one on either side of the pie plate. While looking through the bottom of the pie plate, slowly lower it onto the stencil so the numbers are centered on the pie plate bottom. I eyeball the distance between the top of the numbers and the edge of the pie plate to make sure it’s even all the way around. STEP SEVEN: Turn the plate upside down and place it on the work surface. (transfer tape on top). Using a Silhouette scraper, Cricut scraper or vinyl squeegee, burnish firmly all over. To get nice crisp number edges, the vinyl along the number edges must be securely stuck to the glass. Any bubbles, folds, or gaps will allow etching cream to seep under the vinyl and make for a sloppy etch.
STEP EIGHT: Starting at one corner, carefully peel off the transfer tape, leaving the vinyl on the glass. I find it works best to pull one corner back onto itself and push the transfer tape away from me with both thumbs. If some vinyl persists in sticking to the transfer tape, stop, smooth the transfer tape back onto the area, give it another rub, and lift the transfer tape again.STEP NINE: Double check that the vinyl is securely stuck to the glass. I like to go over all the number edges one last time with my fingers, rubbing out any bubbles or gaps. Bubbles in areas away from the numbers won’t affect the etching, so don’t worry about them.
Now for the actual etching part…
I used this Armour Etch etching cream. See the CORROSIVE and POISON labels and warnings? Read them and follow them to the letter. This stuff is serious, serious acid—the sort of thing your high school chemistry teacher kept locked up. Use rubber gloves and eye protection, protect your work surface, and use in a well-ventilated area for starters. This is also a craft I would not do with children. I just wouldn’t want to take any chances.
I’ve heard that some folks use a spoon or popsicle stick to apply the etching cream, but I worried that such a hard tool might accidentally catch on the stencil pointy bits and pull them up, so I started with a regular soft paint brush, instead. Not a good choice either, as it turns out. It left brush stroke marks in the etching. Ugh. I then switched to a foam brush and have had perfect results ever since.
Shake the etching cream thoroughly like you would a little can of paint. Use a narrow foam brush to dab and gently spread the cream over the numbers in a thick, even coat. Getting it even is important. Uneven coating with some areas thinner than others will result in splotchy etching. Light brushing is fine and helps to create that nice, even, thick coat. Don’t brush vigorously, though, or you risk pushing the etching cream under the stencil around the skinny bits. Leave any crystals on the stencil, not on the glass. The cream tends to shift on the vinyl—for all you science buffs, it appears there’s a little hydrophobic action going on—so once all the numbers are covered, I go around the plate again, dabbing as necessary to make sure everything’s still covered evenly.
Next question… How long to leave the cream on?
Well, on my first Pi plate, I didn’t really know. My bottle of etching cream had obviously been imported to Canada (yup, I’m a Canadian, but you’d probably already guessed that from my accent, right? Hee). The original label had been completely covered by a new bilingual label and, apparently, putting the warnings in French and English left no room for instructions. Bah. In search of the how-to on the internet, I discovered there’s no consensus about how long to leave the etching cream on the the glass. It ranges from a few minutes with mixed results to 10 or 20 minutes and longer. My understanding is that the cream only works for so long—there is a time beyond which it doesn’t improve the etch—but leaving the cream on longer doesn’t hurt. However, if you remove the cream too soon, you get an incomplete etch that’s almost impossible to repair. If I were doing this as a business, I’d spend time testing for the optimal etch time—I’m guessing the sweet spot is somewhere between 10 and 20 minutes. However, with a couple of plates here and there, I’m not too worried about a few extra minutes—better too long than not long enough. I decided to leave the cream on for 20-25 minutes to be on the safe side. After a dozen+ Pi plates, I’ve never had a bad etch.
At the ten-minute mark, I come back and dab to even out the cream again, before setting the timer for another 10 minutes. When it goes off, it takes me a few minutes to return to the work area and don my safety gear. As I said earlier, the stop time isn’t critical, so those extra minutes don’t matter.
Rinsing off the etching cream…
Use the foam brush to gently, gently remove any excess cream. You can return it to the container to be reused next time.
Rinse off the etching cream in a stainless steel or plastic sink. I’m sorry I don’t have any photos of this step, but you have to work quickly and both hands were inside rubber gloves…not so conducive to a quick one-handed shot.
Rinsing is pretty simple, though. I start running the water, then holding the pie plate upside down with one hand, I bring it under the stream and gently wipe off the cream with a few Kleenex tissues in the other hand. When most of the cream is gone I drop the tissues into the sink and continue wiping the glass with my gloved hand. When the cream is all rinsed off, I peel off the stencil and discard, using a small craft knife to lift off the floaty bits in the fours, sixes, eights, and nines. When the stencil is completely removed, I rinse the Pi plate again as I rub it with one hand. At this point, I remove one glove and skoosh a blob of dish soap into my hand and rub it all over the pie plate. Rinse thoroughly, dry, and voila! A Pi plate! All ready for some pumpkin pi(e)?
More glass etching projects:
Framed Horse Head
Whimsical Etched Vase
Nursery “I love you…” in Etched Glass Frame
Flattened Wine Bottle Cheese Tray
Monogram Christmas Balls
Ikea Hack: Etched “Joy” on Tiny MirrorCeramic Tiles
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