How to tell if it has Silicon brake fluid?

[Dr Deuce]

I am trying to figure out how you can tell if the brake fluid is Silicon or not.

The regular brake fluid will burn I believe, so that might be a way.

I have a new (to me) baby coming home and don't want to put the wrong thing in it.

[Marty, SoCal]

See if it mixes with water, Silicon wont mix.

[artificer]

Purple colour?

[W. Winget]

Water and some of it in a bottle, you will see it float.
Can't trust it to be Purple, the color changes after it's been in the system a while, turns a medium brown color usually after aging from what I've seen.
Also could try pouring a little Dot 3 (non-silicone brake fluid) in a jar, then adding some silicon, if they don't mix, you have silicon, if they do, it's Dot 3.

By the way DOT 5 is Silicon. I'm not sure but Dot 4 is a high temp variant of Dot 3 from memory (might be off on that)
You can flush your system and use Dot 5, but some seals may leak due to the Silicone not swelling the material to keep a good seal like the DOT 3 did. I find it (Dot 5) mushy, it's easy to entrap air if shaken, and you will need to let it settle for a long time to get the tiny air bubbles out if it was shaken up.

V/R W. Winget

[motto]

The question has been answered quite comprehensively. The only thing I can add is that Mil Spec silicon brake fluid (the purple stuff) will not mix with the commercially available silicon fluid - Shell Advance Dot5 -. Despite both being silicon fluids they are not compatible.
As suggested, you had best take a sample from the vehicle in question and add small amounts to samples of known fluids.

David