I was wondering if I used liquid emulsion on black glass if the image would look like a positive when developed. Has anybody tried this ?

I don't thing so, black on black???

It should become a positive. That's how ambrotypes were and still are made. The downside to black glass is the cost - it is several times more expensive than clear glass.

It will likely appear as a positive, but I doubt to the extent of an ambrotype. The silver in a wet plate collodion emulsion is kind of whitish under reflected light which enhances the reversal effect seen in an ambrotype. I presume this is the result of the developer used for the process which is ferrous sulfate based. I wonder how liquid emulsion would respond to this type of developer? I've never worked with Liquid Light or similar products.

You can make up a white toner, so yes but you would need to make a negative image as the toning reverses the image tones. Unfortunately you need to use Cadmium Chloride which is highly toxic.

I have tried it, the whit isn't that clean looking though.

Ian