Durable tile marking with iron oxide

Hey folks!

I’ve been experimenting with marking tile with the laser, and have had some excellent results with an iron inlay method:

And here’s the unglazed back of the “day the lord has made” tile, with my initials and the date, so you can see how it looks on unglazed ceramic:

These are handmade tiles, glazed and fired in my kiln, then coated in powdered iron oxide and fused with the glowforge. I got the idea from Rachel Clark’s article Oxide Fusion Printing: A New Method. It’s worth clicking through to her article to get the full details on her process, but the short version is this: once you get the settings right, you can use the laser to inlay a thin layer of iron into the tile. Unlike paint or sharpie, the iron is fused to the ceramic. Much like the bond between glaze and ceramic, it’s stronger than the ceramic itself–you have to chip the tile to remove the iron.

A friend walked me through the chemistry of this a while ago and I believe them, but just for giggles I tried sand sandpaper and a paint scraper on a test tile, and can confirm: the iron doesn’t budge.

The two tiles up top have the iron over the glaze, so I’m not sure if they’re food/dishwasher safe, but for those of us making our own tile, this technique also works under glaze:

This is the product of a lot of ceramics + lasers research and experimentation. I could do a whole separate post about what I’ve learned about laser-assisted ceramics-making, but focusing on this iron inlay technique:

Will it work on commercial tile too?
I haven’t tried it yet, but it should. If anything, commercial tiles might work better, because they’re more uniform in thickness and in the thickness of the glaze.

Is it food/dishwasher/microwave-safe?
As an underglaze, yes–if the glaze you put over it is food-safe, you’re good to go, same as any other iron-based underglaze decal. But this only works if you’re glazing and firing your own tiles.

As an overglaze (on an already-finished tile)–I personally wouldn’t risk it on functional ware (stuff you eat off of), but a glaze nerd may be able to convince me otherwise. It’s perfectly safe for things like trivets and coasters.

Can it be used for tiles that will be installed?
Yes! this is probably its biggest advantage over sharpie/paint methods. Tile is rated for wet and outdoor uses based on how much water the underlying ceramic will absorb, and this process doesn’t change the characteristics of the ceramic.

It’s also safe to use around your fireplace.

Can you do other colors than black?
Rachel Clark demonstrates a range of muted colors in her article using various metal oxides–but it’s worth taking care, as some of these metals are safer to handle than others. You’ll want appropriate PPE, and be sure to double check that the metal you’re trying is laser-safe. Iron oxide is one of the safer ones and fumes are minimal while etching, but these are very fine powders that you don’t want in your lungs. You’ll want to wear an N-95 mask while handling them.

Once they’re dissolved in water, there’s not much risk of inhalation, but fair warning that iron oxide is literally rust and it. stains. everything, including unglazed portions of your tile, as you see on the back of the tile above. (It will also stain your cuticles, if handling it without gloves is a choice you make with your one wild and precious life. Guess how I know).

Can it do raster engraves like a photograph?
I’ve only tried it with solid black designs. I’m not sure how well it’ll handle dot/pattern shading. It definitely cannot handle varying the power for shading–either it’s successfully fused and black, or it’s not successfully fused and doesn’t show up at all.

Where do you get the iron oxide?
Iron oxide is a common ingredient in ceramic glazes and is commonly available from pottery supply shops. What I used for these tiles is Spanish Red Iron Oxide from the Ceramic Shop. (It’s a saturated rust red before fusing, but solid black once fused–the laser essentially creates a “reduction” environment, where the iron oxide heats and cools so quickly that it loses its oxygen and de-rustifies).

The other oxides Clark demonstrates in her article are available from pottery suppliers as well. Some of them are spendier than others.

And now I’ve gotta go to bed, but if anyone else is interested in trying this, I’m happy to chat further!

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Another rabbit hole to explore :upside_down_face:
I for one can’t wait to try this.

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Fantastic! Great work! We await the full write up of laer/tile chemistry!:stuck_out_tongue_winking_eye:

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Nice writeup. There have been other fusion tile projects discussed before, my question is always about the air assist fan: how do you keep the powder from blowing away?

Maybe a good use case for fan reducers?

Edit: found one of the previous discussions.

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Thank you very much for sharing your research and results. The Glowforge is obviously a useful addition in your studio.

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@evansd2 I mixed the iron oxide with water and applied the resulting mixture like paint:

It will eventually dry out enough to start flaking off, but it takes a while–I painted my test tiles in the afternoon and was putting them in and out of the laser into the evening, and the iron was still affixed firmly enough that the fans weren’t going to move it.

The fuse itself produces no detectable fumes–I forgot to turn on the air filter for one pass and still couldn’t see/smell anything. Not that I recommend leaving the fans off; it’s not necessary with the wet mix. Here it is in the laser with the fans on:

I would definitely not recommend trying to use the dry powder with the fans turned down or even off. Iron oxide is more “maybe don’t huff it” than “evacuate the building” in terms of potential toxicity, but it’s still a very fine powder that can contain free silica, aka tiny lung knives. It can damage your lungs, especially over time. For iron oxide, mixing with water will mostly neutralize the risk, but some of the other metals Clark mentions require further precautions.

Applying the wet mix
For unglazed surfaces, the mixture can be pretty thin–the consistency of whole milk. I found that glazed surfaces need a thicker mix to adhere to the tile–closer to acrylic paint or chalk paint. To get it to stick to the glaze, I needed to roll on 3-4 coats with light pressure, letting each coat dry for a few minutes before applying the next. The first coat gave me really splotchy coverage but helped subsequent coats to stick. I may experiment in future with adding a brushing medium (a thickener used in ceramic glazes) to improve adhesion.

It will adhere to glaze more easily with a brush than a roller. Clark reported that the ridges left behind by the brush affected her results, but I found that with the laser focused properly, this wasn’t a concern even with pretty deep ridges (I initially had it set to a material thickness of 1/8" because I had a brainfart, but when I set it it 1/4", which is the actual rough depth of my tiles, it fused through the ridges with no problems).

Clark reports that her mixture flaked/scraped off quickly, but I think she was using alcohol. Using water, I found that once dry, it’d mostly lift if rubbed with a finger or towel, but came off cleanly from glazed surfaces with a damp sponge. It leaves a light stain on unglazed surfaces (of tile; a dark stain on unglazed surface of everything else; my workshop looked like a crime scene. Will definitely do more prep next time).

Cleaning up
The unfused iron is reusable, which is another advantage of a wet mix–less loss. I squeezed the sponge out into a tupperware, and dumped my leftover mix in same. It can be stored indefinitely. If it dries out, just add more water. :slight_smile:.

Protect your pipes
There are lots of ceramics ingredients that can damage plumbing and I’m not sure if this is one of them. I have a bottle trap on my lab sink so I don’t get in trouble with the building owner. But you can also just rinse your tools etc into a bowl or bucket and leave it for a day or so. The iron will sink to the bottom. You can pour the water off the top, then add the iron to your container for reuse.

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:joy_cat::joy_cat::joy_cat:

This is awesome, thank you for sharing the link and your results. My assumption is that they are absolutely fine for food (although why you would eat food off tile? #weneedplates) since after you fire, it is iron sealed in glass, more or less. I’m no expert, just a casual potter and glass worker back in college :sweat_smile: But considering there is a company that literally sells iron fish to be cooked with your soup to add iron to it…

The cobalt would be awesome to try, but I would stay away from nickle, chrome, and copper oxides ;p

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well… now i’m down the rabbit hole with some powder on the way.

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is there a particular reason you recommend against them? she tested red copper oxide, black iron oxide, black copper oxide, cobalt oxide, nickel oxide, chrome oxide, red iron oxide, black nickel oxide (left to right).

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Thank you for sharing this, and it was an excellent write up too. I have a friend with kilns, we may just have to make something.

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From what I remember, cobalt is pretty stable, as is iron. Lots of people have nickel allergies, primarily from cheap jewelry, so I wouldn’t risk that in the powder state, or the fumes from it. Chrome/chromium heavy metal poisoning, hmm, copper verdigris is a poison too. I’m not a chemist, so I don’t know/can’t remember if making it an oxide makes it any safer in general. When I melt glass on a torch, ventilation is very important because of all of these used as colors, as well as lots of others, like manganese or vanadium, and other -iums.

So your ( @leeflowerh ) advice about the N95 mask, personal risk tolerance, and being aware of possible dangers when playing with powders are all good things to take note of. I can’t say if any of the off-gassing would damage the interior of the laser like chloride does, since the laser has far more sensitive components than a kiln does. One of those – take note, it’s a maybe could damage – and possibly do more research for anyone that wants to try this technique. Mostly it comes down to that I would be comfortable with iron and cobalt in my laser, but not the others :grin:

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ok, i get your point. i may have a higher risk tolerance for some of that.

i’ve worked with copper powder and CA, and that’s respirator territory. and i’d treat these the same way. i don’t think anyone should be messing with powders this fine w/o proper mask and ventilation. it’s even a little scarier when you’re pouring a significant amount of super thin CA on top of it (man, that was a nasty reaction).

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@shop Yup, basically a question of training and precautions. Clark was writing for an audience of ceramicists rather than laser nerds, and ceramicists who make their own glazes are used to working with hazardous substances that require careful handling. Ceramics studios are kitted out accordingly, with well-established safety procedures.

I think they’re all fine in the laser, because this process melts the underlying silica more than it melts the oxides themselves (I wouldn’t take my word for it though; @jamely is right about lasers being more sensitive than kilns). The bigger question is whether you’re set up with appropriate precautions and PPE to handle the more hazardous metals.

I’m working in a lab I’ve already set up for ceramics, so I’ve got good ventilation, PPE, a powders booth, and very thorough cleaning protocols already in place. That being said I already copped to forgetting to wear gloves when handling the iron oxide, so I’m not going to write up a detailed description of my safety protocols in case anyone takes it as authoritative. :slightly_smiling_face:.

So it’s not exactly “don’t try this at home,” but as with all laser things, make sure you know what you’re handling, be aware of the risks, and take appropriate safety precautions.

Personally I’m sticking to iron for now, but I do have some cobalt on hand to try when I get braver (FYI for others: cobalt is poisonous as well and requires more careful handling than iron; do be careful with this stuff).

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Also for folks planning to try this: settings will vary based on your tile glaze, but speed 200/ power 15 / 225 LPI/ 1 pass got me the best results on most tests. When using cut/score settings for fine lines, I cranked power up to 20. Power 10 barely adhered at all in any test, and power 25 adhered okay in some tests and completely blew out the iron (leaving a white surface) in others–so you’re looking at fine-tuning in a narrow range of settings.

@ovm.steve, I’m definitely interested in hearing about your results! This post was already kinda long so I left off a lot of other stuff I’ve learned in my ceramics + lasers adventures, but I do have a word of caution about trying to re-glaze commercial tiles: it probably won’t work. And the failure mode is ruining a kiln, so only try it in collaboration with an experienced ceramicist.

I’ll do a separate post soon with the full rundown and you may already know this stuff, but a short version for interested folks:

Traditional ceramics are fired to a range of temperatures, depending on the clay body. If you put a low-fire clay body in a high-fire kiln, it will melt and wreck the kiln. The other issue is that ceramics are usually fired twice: once in a bisque firing that turns clay into ceramic while still leaving it porous enough to glaze, and then again in a glaze firing that fixes the glaze to the ceramic, and fully vitrifies the ceramic. Once ceramic has vitrified, it’s no longer porous, and glaze won’t adhere well. On top of all that, commercial tiles are fired using a different process, so the clay body may not actually be formulated to go in a kiln at all.

There are still options available if you don’t want to make your own tiles and don’t own a kiln, but I’ll write those up in the lasers plus ceramics braindump post.

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my “safety room” is a work table in the front yard covered in disposable paper, wearing a ventilator, goggles, and gloves and sometimes even with a fan nearby. then a mostly-closed box on top of things while they dry (to keep tree droppings and dust off of them). hopefully that’s enough to stay safe.

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genius

:rofl:

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How would you apply the iron oxide to a ready made tile?

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Wow, the stuff I learn on this forum! Can’t wait to see and read more of your work.

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@djfb I wrote up directions in my follow-up comment

The “applying the wet mix” section covers glazed and unglazed tiles–store-bought should be no different than homemade as far as this process goes. Unglazed and matte tiles are easier to coat, but a thicker mix will work on glossy tiles.

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Thanks so much for the tutorial. I’ll be adding this to my list of things to try. Gonna need more paper.

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