Soldering to pots

This is probably a really silly question, but is there a trick to soldering to pots? Do I need to rough them up a bit with some sandpaper first?

Can't seem to get the solder to stick.

On the back yes, rough them up with a bit of sandpaper. It also helps to make a little pool of solder on it, let it cool then put solder your wires, then all you need to do is remelt both lots of solder as you hold the wires in place.

Plenty of videos everywhere and yes, you do need to rough up the surface to remove any silicone and lubricants and expose some bare metal for solder to attach onto. I tend to find it easier soldering on the sides rather than base.
A very hot soldering iron is also the way to go.

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There is two main reasons why you "can't get it to stick"...

First is most pots have a plastic or oil coating on the metal can to prevent rust. This ultra thin coating will often just melt away when soldering but a quick rub with some sand paper or a scratch with a sharp knife will certainly speed up the process.

Secondly, and more importantly, any failure of the solder joint is most probably due the items being soldered did not get to the right temperature before the iron was taken away. On a pot it means the metal can at the point being soldered simply did not get hot enough. This is where the the "trick" comes in, being getting the one spot we want soldered to be hot enough but also to not put so much heat in that it destroys/melts the more heat sensitive parts of the pot. The little $10 soldering iron units of 15W to 25W are only just big enough to do the job by someone with experience. Ideally an iron of between 35W and 65W will make the task easiest. Over 65W will require a skill set that requires considerable delicate practice as there will be a LOT of heat available, often way more than is needed.

For soldering old and corroded pots it is probably best for a novice to take the job to a specialist.

Side note, The task will be simplest and less hassle for a novice soldering student when using 60/40 resin cored solder. Newer Lead free solders are much more critical of temperature and also require notably higher iron temperatures than 60/40 types. If RoHS compliance is needed then get the Lead free solder stuff otherwise stick to the resin cored 60/40 or similar Tin/Lead ratio solder as supplied in all PBG kits or available at your local electronics store...

Thanks guys, will give it another crack.

I had watched a few videos, but I guess I either missed (or they skipped) the bit where they roughed up the pot.

I’ve had trouble with this in the past but on the last couple solder jobs I’ve cleaned the back of the pots with some acetone on a q-tip and they’ve seemed to stick a lot easier

It all helps, but a bit of sandpaper will also clear away any surface oxidation, which a solvent won't do. Tin the pot and the wire first, and then ensure that the solder on the joint isn't all blobby and still mainly on the wire. Once the joint is hot enough, the solder will spread out into a smooth shiny film and that's the time to take the iron off.

Victory! Thanks guys, don't know where I'd be without you all. Got it all wired up no problems

Adding some solder-flux rosin to the back of the pot can also help the solder "take" properly, most of the time just using some sand paper, say anything from maybe 120 grit to 400 grit, to sand the metal so that it's bright and shiny is sufficient, occasionally you'll come across pots where the solder just doesn't want to take properly no matter what you do.