Guitar slides can be purchased cheaply from any music store. But in the theme of the recent blues/cigar box guitar projects, it seemed only fitting to make the real deal--cut off from a bottle (it's the blues--so preferably a bottle containing alcohol). Dr. K isn't a drinker, so this idea kicked around for a while. Fortunately, Thanksgiving yielded a supply of wine and beer bottles, and a wine bottle with the proper diameter was found. I won't give specifics here--test the bottles until you find a good fit. It's totally subjective. The diameter, length... are all a matter of personal taste.
Step 1: The Need
In the spirit of traditional blues, junk and recycled material should be used whenever possible. A perfect example of this is a glass bottle neck guitar slide. My first idea was to try the truly HARDCORE method, playing with the back edge of a straight razor, but I'm clumsy enough that trying to manipulate a razor in my left hand, without slicing my fingers off, made me reconsider! I had been playing with a piece of copper tubing, but it seems far too soft to sound good with wound steel guitar strings.
If anyone is interested, the guitar pictured here was build from old thin plywood boxes and a piece of hickory from a discarded post hole digger. It features a recycled aluminum bunt pan as a metallic resonator, and pieces of bone for the nut and saddle. It has a cool sitar-ish buzz that sounds really cool (sound bite at the end) (in standard GDG tuning CBG tuning)
Step 2: Select a Bottle
My Thanksgiving hosts, whom I had largely never met, seemed a little confused why I was sticking my left hand ring finger into the recycling bin :-) . (Dr. K has a host of strange hobbies--the most important being the quest for useful junk).
I prefer a straight slide. Notice from the photo this one necks down slightly at the opening on the inside, but bulges out on the outside. I decided to cut the middle of the neck out requiring 2 cuts.
Step 3: The First Cut
A standard hardware store wheel glass cutter was used. The cut was done free hand, using the lip in the neck as a guide to keep the cut straight. When using a glass cutter, exert enough pressure while cutting that you can hear a high pitched scratching noise. You want to make the cut in on motion, or if you have to stop and re-align the bottle, do not overlap the cuts too much. The process could be made easier by holding the bottle in some kind of right-angle "jig", even a corner of a door frame or something, holding the glass cutter, and rotating the bottle. I actually cut this sitting on my couch, free hand.
Glass is a strong and hard material (perfect for a slide). But it can be weakened, and then by applying some thermal shock, it can easily crack. That's the trick here. Cut the bottle, then submerge the neck in boiling water for about a minute, and finally plunge it into ice water. This took two tries, but then there was a satisfying "tink!" and the end of the neck fell free, leaving a nice smooth cut. CAREFUL! It's a hard, sharp edge! (more on that later).
Step 4: The Second Cut
The second cut did not allow a nice straight guide for the glass cutter. To keep the cut straight, I wrapped the bottle neck with masking tape. Then about a milimeter away, with another turn of masking tape. This helps guide your hand, and also protects the glass from scratching into the bottle where it shouldn't. It is possible that an errant cut could cause the bottle to crack at a weird angle. Again, cut around the neck with one cut. Don't go over the cut repeatedly. If there is a nice, white, visible scratch around it, that's enough. Then remove the tape, and get the water boiling again.
Step 5: Smoothing the Cuts
Both ends of the slide are razor sharp glass. You really need to polish or smooth them to break the edges. Any sandpaper (garnet, silicon carbide...) will be harder than glass and so can be used to polish and smooth the surfaces. Since the ends are not perfectly square, I first polished the outside edges by wrapping the sandpaper (80 grit here, because I had some) around a piece of wood and went around them several times. Then I wrapped the sandpaper around a small diameter marker, and went around the inside several times. Finally, I went around the flat surface. Take you time, and continue until the shiny, cracked surface gives way to a nice evenly scratched surface.
Step 6: Finished Guitar Slide
Well, the slide turned out beautifully. Unfortnately, it feels too big and sloppy for my small diameter fingers! That's ok, it's always a cool gift to give to a friend, or to have a spare laying around so your friends have a selection for an unplanned jam session.
I had been using a length of copper pipe for the slide, which kind of "grabs" the steel strings I like to play with. The obvious scratches on the copper let me know that the strings are actually cutting into the copper slide. I really like how this one sounds, and it has far less "buzzing" when sliding it.
Forgive the terrible guitar playing and sound quality. Recorded in one take, live to laptop!