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100% acetone works. "Maximum strength" nail polish remover, $2.50 in the beauty aisle.
I put the image on the mug around 10 times before I got a good transfer. Sometimes putting a stencil on takes a long time to get just right. It is worth spending the prep time upfront to get the best result. Here is what I learned:
1) Since the metal is grey and shiny, painting the mug with white watercolor paint beforehand adds contrast, dulls the surface and adds tooth to help the print stick and show up better. Also interesting, removing the toner with acetone will not remove the watercolor if you don't rub too hard. I also tried a poster paint but the watercolor paint proved to be far superior, because it dries without the brush stroke texture and washes off easily. I will keep a tube of cheap Cotman white watercolor on hand from now on.
2) Choosing and processing the image is critical. A simpler design in pure black would have been best, but I got my heart set on a piece of concept art so that's what we're doing. Trying to transfer something with many different levels of grey will be hit and miss and probably an exercise in massive frustration for someone with less experience reading shitty images on imperfect surfaces. If you are comfortable sketching people from life in ink (no erasing, no foundation pencil), you should be able to handle photographic source material and have the hand-eye coordination to make up for any bad spots in the transfer. If the idea of drawing something with no eraser sounds iffy, def avoid anything with grey tones. Plain symbols, lettering, black and white inked art like comic book art - these will be easiest by far. Don't talk yourself into text smaller than 8-10mm.
Tweak the contrast of the image and potentially create white borders around any low contrast subjects for better visibility. I also found that reducing the opacity of the image to around 80-90% helped, because too much toner causes problems. Dark dark greys transfer better than solid black, especially in a filled area. Mirror the image or it will be flipped in reverse on the item. If you want straight line borders on the object, might be easier to draw it on with a sharpie than try to align the transfer perfectly. A rubber band can be used to make a guideline on cylindrical objects.
I inverted my image to negative so the white parts are black, and then I engraved where there is toner. There are pluses and minuses here. This mug is much shinier and reflective on the engraved areas than my tester object, so it takes the place of either pure black or pure white depending on the light. I may not have needed to invert it. I'm not 100% done so it's hard to say. Just fyi this may depend on how the material of your specific item engraves. Will the cuts be very shiny or frosted? (A smart person would have a bought a spare to experiment on first.)
3) Print out a fresh warm copy, cut it out and tape it as flat to the surface as possible. Acetone will not get under the tape so don't cover a part of the image. Soak a cotton pad in acetone. Work from one side of the image methodically to the other, soaking the paper so the design bleeds through. Do not go back over areas. The paper will expand and warp as it absorbs the liquid and if you go back over, it won't match up perfectly and create a slight double image, which is garbage. Just soak it good the first pass and leave it alone. Let the paper dry completely on the item. Undo the tape and take it off. If you don't like what you get, wipe the toner off with acetone (gently, to preserve the watercolor layer) and repeat the process with a fresh copy.
The toner transfer is more durable than expected. Gentle handling or wiping won't smear it, which is FANTASTIC. Very very pleased with this new trick.
Engraving stuff notes:
- Start with a section that will grab the least amount of attention. People 'read' an image top to bottom, left to right, zeroing in on faces, hands, feet, cleavage and lettering. Best chance of hiding beginning hiccups is by starting at the least interesting bottom part of your design.
- So far the most useful bit shapes for the rotary tool are the round ball and dome tip cylinder (like a lipgloss applicator shape). A bullet shape would probably work well too. Inverse cone or wheel shapes are suited for straight lines. Thin pointed bits look like they'd be the obvious choice, but due to the rotation of the tool, the point has the least amount of bite and skitters around the most. It is better to utilize the side of the bit than the point. I've been positioning the tool at a 45deg angle or less to the object and working lines inward, toward my body.
- I've been using a cheap set of assorted diamond bits ($15ish off amazon). The cuts on this mug are surprisingly shiny, almost laser cut, like drawing with liquid silver ink on grey paper. The one bummer is there's not much variety of texture/shading possible. I ordered another set of bits of different materials for grinding/polishing and I want to see if I can get different textures to better simulate different values from the original art. I checked into stainless steel patinas, but so far no small amounts for a tiny project like this. Another idea to try is using wire whisk bits to get a streaky brushed texture with another thin piece of metal as a handheld frisket, sort of like with airbrushing or spray paint.
- Direction of stroke and the rotation of the tool have to match to create a uniform light reflection. If you change your approach, you change how the light strikes. So if you're holding the mug a certain way to start a section, you have to keep holding it and the tool that same way for the entirety. You can't turn the mug upside down to finish a line and have it look the same. It may look dark when the rest is bright.
- Speed of the machine and speed of hand movement matter. Move too fast for the machine and get a skittery dotted line (cool effect if you want it, like blackwork tattoos). Slower speed for larger diameter bits, because the outer cutting edge will be rotating faster. Slower bit speed, slower hand movement. Lighter pressure is best - you're just skimming off the top surface of the metal, not drilling a hole. Let the tool do the work. Move in lines, one direction. Circles and ovals don't give uniform results.
- Set your station up with good lighting. Have eye protection, a mask, snug vinyl or nitrile gloves (will protect your hands from accidental slips of the tool, preserves the toner image and helps with grip). A foam pad to rest the item on and absorb vibration. A clamp to clip the excess cord to the table so it doesn't drag at the end of your tool. Foot pedal control is nice to have. Paper towels, because what craft project doesn't need paper towels. I stuffed the mug with a dishrag to muffle sound, but due to the double walled construction I am not sure it helps much. The sound level is quieter than a kitchen blender but louder than a sewing machine. There will be some metal dust.
I should have finished this yesterday but I've been feeling foggy and tired, stuffed ears, like I'm coming down with something. I was waiting for the new bits to arrive. Amazon promised yesterday, then delayed to friday, but delivered yesterday anyway while I was napping. I only napped because I thought the package wasn't coming. Annoying.
For spouse's mug I flipped through a book of concept art from The Mandalorian and picked out a piece that shows the title character firing an ewebb heavy blaster cannon. Concept art is great because it always has exaggerated lighting and high drama. It's simpler than true photorealism, but it has all the punch. The great part of masked star wars characters like stormtroopers and Vader and Boba Fett is you don't have to worry about getting a good likeness. The terrible part of masked star wars characters is you have to draw a shiny symmetrical helmet.
This one, except I changed the background to add in the skyline of the town for extra interest.
It's going to be rad as hell, especially if I can figure out how to do some additional textures and shading. I'm in that weird middle stage of a project where it's unclear if you're going to meet your own expectations. You haven't screwed up yet, but your perfectionist streak is running berserk. Worst part of a project. Right now I love it 49.5% and hate it 50.5%. When the mug is done I will love it 50.5% and hate it 49.5%. This is the way.
