Well, yes! You can use the Ti02 on tile and transfer a photograph over.
I personally haven't seriously tried to do this but I have seen pictures of it! ðŸ¤
Anyway, at this point from part 1, there should be a good power/speed setting selected that does a good job with turning the Ti02 coating into a black that is fused into the tiles glaze layer.
There were two ways to get the Ti02 coating discussed. First was with a mixture of the Ti02 powder into a binder, in this case PVA glue. That was brushed on in several layers. Best thing is when finished with the laser, you can just set the tile into a pan of water until the glue dissolves then rinse off the scum.
A scrubbing with a scour pad (I use the yellow sponges with the green scrubby side since we seem to have 10 billion of them). Un-blackened Ti02 powder will crust up near the etched areas and may require some scraping.
This method works excellent for getting a line art image onto a tile, but it is difficult to get the even layer required for a photograph.
If you aren't into mixing stuff up, you can just use a spray can primer with lots of Ti02 as an ingredient. In the last part I used Rustoleum 2x Matte white. It worked well, but then I found that the 2x Flat white has an even greater concentration.
Since it is sprayed, getting even coats is easy.
Finding the Machine Settings
Since the laser can only turn the Ti02 black, to get a shade of grey a technique called dithering is used to trick the eye into seeing grey versus just black. This involves varying the number of black spots in an area of white tile glaze. The more black spots, the darker your eye will interpret the area to be. This all happens at a very small scale with very small dots.
Even though the laser can focus to a small point, melting and fusing the Ti02 creates more of a "blob" than a dot. Also is the issue that a diode type laser has a rectangular spot. The laser needs to be told how to make that spot the correct size given that a blob is being created verses a nice and crisp dot.
The photograph is burned onto the tile by scanning or rasterizing. There are settings to tell the laser how many of these scan lines to create per inch. If the lines are too close together, the melted Ti02 will bleed over to the there lines and really reduce the ability to create detail. An optimum Lines Per Inch (LPI) setting is needed.
Fear not, this video explains all this much better than I ever could:
I ran my own test to see what LPI setting was best. I also created a second tile running up to 300LPI
Here is a closeup of the 300 LPI:
Solid black. We are looking for scan lines that are just touching so this setting is too high.
Here is what 115 LPI looks like:
See the white between the lines? This setting is too low.
Best was found around 160 LPI:
If you look hard enough, you can tell there are lines, but no white space between.
Set LPI=160
Now for the dots. Normally the laser software will tell the laser how long to make a line. We need someway to measure that line and compare that length with the length we specified. With LightBurn, this is called "Dot Compensation (DC)". I ran a test pattern with DC running from 0.10mm (cut line 0.10mm shorter than commanded) down to 0.03mm.
This is a closeup of 0.10mm
The corners of the squares should lust be touching so the lines are a bit short. Note that the lines have rounded ends.
At 0.03mm:
This is much better!
DC=0.03mm
Watch the video and you will understand the reasoning and process behind all this!
