[mattmoose]

I am planning on following this guide to make my watch waterproof. I would also like to dye the oil as they did in the guide. My question is: what dye did they use? Was it something like Sudan IV? If so, where can one obtain some?

thanks!

[Enthalpy]

Welcome, mattmoose!

Not the answer you expect, but:

Mineral oils are unhealthy. Depending on the source of crude oil and its processing, they contain polycyclic aromatics and many more compounds, of which some are carcinogenic, allergens, or just irritants. I wouldn't put any for years near to my skin nor under my nose.

To the very least, you should choose said mineral oil with great care. Different names exist and are loosely used, like "paraffin" and more. Some are meant for skin contact. Things like condom lubricants.
https://en.wikipedia.org/wiki/Paraffin
https://en.wikipedia.org/wiki/Liquid_paraffin_(drug)

It would be hugely better to take a vegetable oil. Olive oil is imperfectly stable, but no air is supposed to enter the watch. Peanut and sunflower oil are even less sensitive to air.

Heating the oil to +50°C makes it thinner. The intention can be to let bubbles escape more easily and help the oil wet all surfaces.

[mattmoose]

Thank you for the follow up Enthalpy. I didn't realize there were health risks associated with mineral oil.

Will vegetable oil go rancid after a while?

Also are there any known health risks with sudan stains once they have been added to the oil?

[Enthalpy]

I'm confident about vegetable oils. A few ones are known to react with air, but sunflower and peanut oils are rather unreactive, and the watch is closed. I used some in lieu of thermal grease at a processor, at heat for years, an it didn't smell. Just experiment, if these oils don't fit, you can still replace them with a more expensive silicone oil.

I ignore dyes very accurately, so hopefully someone else answers.

[OrganicDan96]

what about unscented baby oil? its designed for skin contact