How would you seal/protect gold plated fr4 and alu pcb coasters? Ideally foodsafe.
Got a favorite Epoxy pour, or XTC-3D, or something else? Gold plated etching is hard to see, so finish that isn’t too glossy would be nice?
Turns out v1.0 Jackpot PCB is almost Coaster sized. Some PLA/Epoxy could help square it off, and seal the vias.
Using this gifting season as opportunity to learn and try out some stuff.
For PCB with electrical components would use MG Chemicals 422C Silicone Conformal Coating.
For a coaster I wouldn’t personally worry about it being food safe necessarily. In the past, I’ve just given PCBs a coating of gloss clear acrylic from a rattlecan to stop them tarnishing. Does make them a bit shinier than I’d like and I’ve never revisited it. A wipe on poly would likely work just as well, too.
(edit: This is actually pretty similar to the process for conformal coating a PCB for moisture resistance etc. You can get specific products for that purpose that are basically just a specifically formulated clear acrylic, often with additives that fluoresce under UV for post-application inspection)
I made a 3D printed pepper grinder body in the past and used regular 2-part epoxy to seal it in a hopefully food safe manner. I changed the ratio to be slightly resin rich (Edit: had this the wrong way around), then worked to ensure that it was super well mixed. No idea if that’s actually a good idea or not, it’s just a trick I read about for making custom water tanks on a boat building forum maybe a decade ago.
I love west systems epoxy with their metering pumps. But it’s not good safe :(.
Same with modgepodge. There was some counter top epoxy I have used in the past but it can yellow pretty quick.
I wonder how automotive clear coat would work.
I agree entirely - without stating the obvious it’s probably best not to use a water-clean up finish. Sometimes the gloss will bring up the etching, sometimes it will hide it. If you have a part to try or can just wet it to see - if you are lucky the engraving will pop and you can use a high gloss pouring resin for a “cast in” effect.
I think unless you have stock at hand, you can ignore the following but it’s there to add some seasonal spice to the thread!
There are epoxies and epoxies - in a past life I used a lot of them and was a manufacturer’s agent, but that was a long time ago so the usual cautions apply when reading stuff on the internet including stuff written by me:
Any epoxy is probably OK for a coaster, but not all will have that nice finish you are looking for.
Any epoxy suitable for water tank lining will be fine. My strong advice is to NEVER change the ration of an epoxy mix. While a polyester or other two-part compound relies on a catalyst to “kick off” the hardening reaction - it’s a bit like honey crystallisation but please don’t quote me, I just don’t have a better analogy. Adding more catalyst to polyester will reduce the curing/working time.
Epoxies are a different family - the two parts bond chemically so an imbalance will mean a weaker/less reliable brew. More “part B” won’t affect the curing time at all either.
This is particularly the case for watertanks where you don’t want to have any epoxy “taste”, but I suspect the “epoxy” spoken of above was actually a polyester.
Note that most epoxies are not UV stable so make sure you are using one with UV inhibitors - furniture pouring resins usually have them.
The products being discussed were definitely true epoxies, as was what I used. I also mis-remembered and went back to the original e-mail where I was discussing it with the person I had made the part for. I had mixed it hardener-light, resin-heavy by ~10% or so, making sure to change containers a couple of times to ensure that the mix was as consistent as possible. This was also for something where contact with food was more likely than with a coaster.
