18ct solder on 9ct gold?

[Niamh]

Hello,
I work alot with yellow gold mostly 9ct, My friend has stopped goldsmithing now and gave me a syringe of 3g 18ct yellow gold solder paste from cooksongold unused.
Can i use this on 9ct yellow gold or red gold or will the colour difference it be very obvious? thank you

[Dennis]

If the parts fit closely, the colour won't be much of a problem at first, but 9ct tarnishes quite quickly, leaving the solder potentially brighter. Dennis.