Kurt Cobain

According to a Guitar Geek diagram, Kurt Cobain used GHS Guitar Boomers 0.10 strings.

Dean Markley (Light Top/Heavy Bottom) Guitar Strings.

The only piece of information in regard to strings coming from Kurt himself comes from one of the interviews from the Musician magazine, in 1992, where Kurt mentioned that he’s using actual piano strings for low E and A. I use piano wire for guitar strings, ’cause it’s a lot thicker. I buy it in bulk, in these big long tubes, and just cut it to the length of the guitar. They’re thicker than the thickest guitar gauge that’s available. I don’t know what the thickness of ’em is anymore – I can’t remember. I use a really thick E string, and then a smaller size A. A few of the others are guitar strings – I think I use Dean Markley because they’re the cheapest.

However, this was most likely just a joke that over the years developed into a legend. Piano strings would be impossible to fit on most of the guitars that Kurt was using at the time, and if he indeed wanted thicker strings, there were easier ways to achieve that.

One of them would, of course, be to just use a heavier set – which is most likely what he did. Based on the photos, and a statement from Ernie Bailey, Kurt actually used Dean Markley LTHB set (.010, .013, .017, .030, .042, .052). For strings, he used .010-.052 Dean Markley’s (the red pack).

In case you’re looking to buy the same set, unfortunately, it’s no longer being made. If you want something similar from Dean Markley, their Blue Steel heavy set (10-52) should do a pretty good job (same principle as the original – Light Top/Heavy Bottom)

he used dean markleys .10-.52 gauges according to dean markley themselves

It shows here he used Dean Markley Gauge .10-.52 strings

Envelopes for strings M56P, M35P and M26P were included in the June 19, 2020 auction of Cobain's Martin D-18E, lot 742 of the "Music Icons" auction (#3261).

A receipt from around 1990 confirms that Kurt Cobain purchased Dean Markley Electric Guitar NickelSteel Light, .009 - .042 strings.