Does anyone know why scanned negatives sometimes have these multicolored wavy lines in them? and how I can get rid of them/ avoid them?

Those are called newton rings. You can get anti-newton ring glass to minimize it.

http://www.betterscanning.com sells glass anti newton ring inserts that fit inside their custom film holders, but that can get expensive.

Also make sure your film is as flat as possible when scanning. The less curl, the less likely you are to get those lines. Check to make sure your negs aren't coming into contact with the scanner's glass. Scanning with the emulsion side down may help as well.

Even the special glass is prone to newton rings, these have been a huge problem for me. Whenever I get a roll back from the lab I cut it into strips and put the negatives inside a hardcover photo book. Add weight and they'll be pretty flat in a day or two.

Thanks for the info. You think I could just cut a normal piece of glass to help keep the negs flat?

Posted by willskith Even the special glass is prone to newton rings, these have been a huge problem for me.

I have the betterscanning inserts. Only time I get the rings is if I don't have the glass facing the right side up.

Posted by Adv.Pack Thanks for the info. You think I could just cut a normal piece of glass to help keep the negs flat?

You could try using good quality anti-glare glass. Any local framing shop should be able to cut you a piece for a reasonable amount of money. You'd still need a way to keep the film off of the scanner's glass though so unless you have a holder for it, you won't be any better off than you are now.

What scanner are you using, anyway?

Im using an Epson 4490. I'll probably just try flattening my negs more before I scan.

Good to know there is a solution, I've had this same problem before

Always experienced those when my film touched the scanner-glas.

I use now the betterscanning.com film holder without the ANR glass. Since it is often difficult to get a flat film I usually insert the film with the bulging side up and fix the film with the supplied T-Locks. Works like a charm!