E TwentyNine wrote: ↑lot_lizard wrote: ↑ I did try dye-subbing with a crayon the entire cap, and then brought back an ivory letter with very good results (without going very deep). I would be taking more pictures of all of this, but they are just turning out "less than reality"... so hesitant to upload.
Upload them anyway. And I've been meaning to ask - how do you dyesub with a crayon? How did you do the early MF key with crayon creation?
I'll dig the camera out and see if I can do a little better job. All photos so far have been shot with a phone.
Verbose "nerd speak" to follow... proceed with caution.
I'm using the term "dye-sub" VERY loosely just because that is the process we are familiar with. This uses a very different transfer process, but yields similar results. In dye-sublimination we use pressure to direct the "dye gas" after it leaves the transfer sheet. The heat required both turns the dye from solid (on the transfer sheet) to gas, but it also de-bonds the polymer enough to allow absorption without being so hot that thermal degradation occurs. When the polymer cools, the bonds are reformed. The only real downside to the process is that some of the gas is diffused to the surrounding polymer (no way to create truly hard lines).
Keep in mind this next part is with a crayon (not an ideal pigment additive).
A laser (when engraving/cutting) is actually vaporizing (boiling) the solid through a tiny hole (the resolution of the beam). In an ideal world, you want to completely cut/engrave everything on a single pass because the composition of the material might change when cooled and cause reflectivity on the next pass (this is ALWAYS minor, EXCEPT IN OUR CASE). For my little silly experiment with the crayon, I am changing frequency/power of the beam in such a way that the underlying PBT is never vaporized, but becomes a liquid crystalline. The crayon has a much wider temperature range where it remains a liquid (lower melting point / higher boiling point). The beam is able to shoot through the liquid crayon, and heat the PBT without impacting the chemical properties of the crayon melt. Eventually the PBT melts enough to absorb the pigment and we move the laser to the next "keyhole". Back to doing in one pass, since we are mixing materials, we now have a different makeup that we would need to melt since the crayon is now physically mixed with the polymer (bonding is very different than with the PBT alone). So all of the settings would need to be adjusted for the second pass. This is different than engraving say metal where you would just keep pounding away. If we hit the PBT too hard, it vaporizes, but the vapor would have no where to go with the crayon melt above (creating a discolored mess).
So we are similar to the "dye-sub" technique, with a couple distinctions...
- pigment is transferred as a gas in dye-sub, liquid in our case
- dye-sub uses pressure to direct the gas, where we essentially just rely on gravity (think water seeping into dirt on a molecular level)
- dye-sub diffuses pigment into unwanted areas because the entire polymer is heated at once, where we only heat the size of the beam
Again... we will find proper additives for pigment that were made for this process. I doubt the crayon will yield the best results possible. Just a fun experiment.
). We are onto something I think
