One of my sets of Denise needles from 1983 (white with pale blue cords) has many tips that feel quite rough, no longer slippery. I have tried buffing with nail buffers, but it has no effect. Also notice that some tips retain a bit of color from the yarn last knitted that is NOT removed with buffing. Anyone have a suggestion?
Sarah's idea of varnish would probably help a lot. I was going to suggest clear nail polish followed by sanding, but varnish would probably be better!! that would prevent some of the staining and the sanding should smooth them out.
but if you can be without the needles for a while sending them back might be best. (they will probably just ship new tips. cheaper for them than rehabbing.)
did I say one project at a time?
Needles don't live forever and these have had a long and useful life.
I don't know for sure, but in most cases a "lifetime guarantee" is a guarantee against manufacturing defects, not wear-and-tear from normal use.
But the Denise people have a reputation for great customer service. If they don't actually replace or refurbish the worn-out tips, you can buy replacements for a few dollars. Weigh the possible cost against the time it would take to try refinishing them yourself, and the chance that varnish or nail polish or whatever would end up flaking into your yarn or making the problem worse.
I think that when the Denise product was resurrected a few years ago, the manufacturing processes were improved. Current needles and cables have a higher grade of finish (smoother, slicker, better joins) earlier models.
I'd be curious to compare my old, thoroughly used set with what's being sold today. If they are really better, it might be time for a replacement.
Denise had a problem with the cables several years ago -- they became sticky in use. As I recall, the company admitted the problem publicly and invited anyone who had the defective cables to return them for free replacements. They changed manufacturers and I haven't heard of any problems since.