This method builds on the Norton White Tile Method (NWT) which fundamentally has been based on using Titanium Dioxide (TiO2) in white paint products to create indelible markings on the surface of tiles. The principal component method removes the need for a paint product and provides a method to directly apply TiO2 to the tile for engraving.
The benefits to this method are once the TiO2 has been applied, the tile can be immediately put under the laser, there are significantly fewer fumes, and no harsh solvents required to clean the residual TiO2 from the surface of the tile.
Materials Required: Powdered TiO2, ethanol, kitchen scale, airbrush, air tight containers that will not be degraded by ethanol.
The primary ratio that was used was a 1:3.5, TiO2 to ethanol solution. This ratio was chosen based on the suggestion in this thread: https://www.researchgate.net/post/I-have-TiO2-powder-and-want-to-dissolve-it-Which-solvent-can-play-the-role
I found that adding an additional splash or two of ethanol helped reduce the clogging and splattering with the airbrush.
To initially mix the the TiO2 and ethanol I poured them both into a wide mouth mason jar and used a pestle to crush any clumps while stirring the solution. The resulting solution should have an opaque white hue with no visible granules and a very low viscosity.
To prepare the tile for the application of the TiO2 solution I wiped the tile off with a dry cloth.
Once the solution has been mixed it is ready for application to the tile with the airbrush. If you have stored extra solution after using some, give the container a good shake before use to make sure that any sediment is fully dissolved in the solution.
I used this airbrush and applied three full hoppers of of the TiO2 solution to the tile using the lowest pressure setting on my compressor (15psi). *This should be done in a well ventilated area (See note at bottom about TiO2 toxicity)*. due to the high evaporation rate of ethanol, when using the airbrush it dries almost immediately after landing on the tile. For spraying the tile I held the airbrush ~6-8 inches (15-20cm) from the surface of the tile moving in sweeping or concentric motions being sure to cover the edges thoroughly. Be sure to take steps to reduce splatters, as an unfortunately placed splatter can ruin an engraving if you are unlucky. Cleaning the nozzle regularly, running lower psi, and thinning the solution with more ethanol should help reduced splatters. In addition to those steps also make sure dried bits and flakes are for the most part removed from the solution, as they will clog the airbrush. After the airbrush has developed a somewhat substantial crust of dried TiO2 it should be rinsed out, because as mentioned just above the bits and pieces tend to clog the airbrush. I have found that keeping a paper towel or rag on hand, and while taking short breaks from spraying, simply wiping the nozzle of the airbrush significantly helps to reduce splattering. Also being cognizant and wiping away any dripping from the hopper before it drips off the airbrush.
Once the tile is coated it will have a noticeable matte look to it and there may be some small visible granulation’s on the surface of the tile. This is expected and ok. The ethanol should be entirely evaporated leaving only a very fine powder coating of TiO2 on the surface of the tile. The TiO2 should have a decent hold on the surface of the tile and not blow off without some considerable effort. I have found that blowing off the tile using the airbrush on the lowest air pressure setting, while the hopper is empty helps to further reduce the granulation on the tile. There should be no loose powder on the surface of the tile. The powder does wipe off very easily however and the tile should be handled carefully by the edges as a slight brush has the ability to take the coating off.
There are few to no differences in the actual engraving of the NWT principal component method, and the NWT traditional method. Be sure your drag chain does not brush the surface of the tile during engraving as it will take the powder coating off and likely ruin the engraving. I found that my settings for the NWT traditional method worked well with the principal component method. Running an Ortur “15w” (~4.5w) LM2 at 750mm/min 80% power I was able to get very good results. *Note vaporizing TiO2 with a laser may produce “Hazardous decomposition products:Carbon oxides (CO, CO2)” https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatory-documents/sds/chemicals/chemicals-t/S25818.pdf and you will want to have your ventilation system running like you would while running the NWT traditional method.*
This tile was ran with two hopper fulls and was the first to produce results comparable to spray paint. The image was chosen as its a finely detailed vector and allowed me to see how consistent the application was over the whole tile.
While the results with two hopper fulls were good, I found that three is more consistent and produces just a bit darker fuller black.
Limited raster engraving has been attempted and the results showed promise and will be the next stage of serious testing now that a solid consistent method has been developed.
Once the engraving is finished the tile can be taken to the sink and rinsed off under the tap with some light rubbing by hand or cloth. This should remove all of the excess TiO2 leaving you with a finished work piece. If the back of the tile gets wet it should be left to air dry as it is a porous surface and will absorb some water.
Attempted Application Methods
Several methods of applying TiO2 were attempted before the airbrush was decided upon as the better method. Most of them worked to a varying degree but had strong enough drawbacks to make them less than ideal.
Attempted Application Method #1: Paint Brush
This was the first method I tried, when the coating was right the results were quite good, but getting it consistent over the entire tile proved difficult. The image below is of a tile where the TiO2 solution was brushed on, and the odd gradients can be pretty clearly seen. Also the blacks are not as dark as I would have likely them to be.
Attempted Application Method #2: Pouring
In order to get an even layer over the whole tile I tried taping the edges and pouring the solution onto the surface of the tile. This produced an ok result, however it tended to promote granulation. Which then led to a final result having a sort of fuzzy and unfocused look to them. In addition to the fuzzy look the areas of solid black there tended to be a “salt and pepper” effect where the larger granules seem to prevent the laser from hitting the surface of the tile. I attempted double poring as I hypothesized that it might not have been a thick enough layer to cover the surface of the tile adequately. This was wrong as it actually made the entire image worse .
This tile was ran with a second application of the pouring method, clearly it did not turn out to the same quality as many of the other tiles.
Attempted Application Method #3: Hand Spray Bottle
This method tended to produce more consistent results than the paint brush and a less fuzzy result from the pouring, but it did not eliminate the fuzzy or salt and pepper effects entirely.
Since the release of the original version of this method I have received some really great input from the laser community at large and I will continue to update and refine the method as further experimentation happens. Some of the things that are currently on the forefront of the docket are trying to figure out good alternative application methods. Particularly using paint rollers, and spin coating. A member of the LightBurn forum identified this article with provides great in depth information on spin coating TiO2 onto ceramic wall tile. https://www.worldscientific.com/doi/pdf/10.1142/S2010194513009951
I have also begun the process of testing raster engraving and will be providing updates as I start to get some consistent results one way or the other.
It has been historically accepted that TiO2 when inhaled is carcinogenic, some information was brought to my attention on the LightBurn forums that tends to contradict this notion. “The epidemiological investigations evaluated the mortality statistics at 11 European and 4 US TiO2 manufacturing plants. They concluded that there was no suggestion of any carcinogenic effect associated with workplace exposure to TiO2.” https://academic.oup.com/annweh/article/49/6/461/176940
While there may not be strong evidence at the moment that TiO2 is explicitly carcinogenic, that does not mean it is healthy to breathe. Any micro particulate is not good for the lungs, especially one that is riding on pure or nearly pure ethanol. Therefore I would still strongly suggest treating it like any other chemical or mineral spray and taking steps to reduce the exposure to the inhaled particulates created while working with this method.