How to pre clean a very dirty LP before Ultrasound Machine?

Thanks so much for all the great advice!

Whats then best solution for dissolving organic contaminants? like mold etc.?

@slaw - what steam cleaner do you use?

enzyme cleaner, audio intelligent, mofi 

Just put them in the US cleaner, clean, and rinse. Never tap water. Use the US cleaning water until it’s obviously filthy, then change.

You may have to clean each record twice. Note that not all US machines are created equal: power, frequency, reliability. Also, note that the distance between records is important - the wavelength of sound in water is 1.5" at 40KHz. Cleaning works best if the distance between records is at least that much.

For chemistry, I use distilled water and VersaClean from Fisher Scientific. It’s a cleaner recommended for US which is specially formulated for plastics. The benefit of using Fisher is that it’s a scientific supply company, and their stuff has to work as advertised, or there is hell to pay. Hell administered by the Military Industrial Complex - trouble that nobody needs. Of course, you could use Joe’s Guaranteed Vinyl Record Goop, but why?