Glass Guitar Slides

Glass guitar slides have been around longer than any other guitar slides. They stem from the roots of slide guitar, the bottleneck. Glass guitar slides are typically cheaper and lighter. Neither of these are exactly bad traits. They are cheaper because of material costs, not because they are lower quality. Though, not all glass guitar slides are equal. Some are made with pyrex and others are made from real heavy duty glass. The lighter material is great for lower action guitars. This is a great choice for players who want to play slide on their normal acoustic guitar or electric guitar.

Slide technique and regular playing techniques can be applied easier with glass guitar slides. When playing slide method on a regular guitar, guitarist don't want to apply too much pressure to the string. If the strings make contact with the frets underneath, Then fret noise will occur. This is generally not a desirable sound. Using a lighter slide, like a glass bottleneck slide helps prevent applying too much pressure to the strings. 

Most electric slide players that I've seen, use a glass slide. Some examples of electric slide performances that I really like are:

Eric Johnson's performance of SRV, which uses very little slide but is a good example of incorporating a glass slide into regular guitar technique. 

Here is Eric Clapton performing "Tusla Time" with a glass slide on his Strat.

As you can see, glass guitar slides on electric guitars sound very good. Slide itself is pretty simple. Lay the slide on the strings. Move up and down the neck. It seems very simple at least. Your technique is very important, however. Your ear plays a much stronger role in slide guitar playing than in regular playing. You have to listen very closely to the note you are playing because, since you aren't fretting the note, it's easy for it to be flat or sharp. Also a major factor in good slide playing is noise from other strings. Muting string that you don't want to hear is important. You can use palm muting with your strumming hand along with muting from the non-slide finders on the fretting hand.

The light weight of a glass guitar slides is hard for me to get used to. I prefer the heavier guitar slides. I've never actually played a glass guitar slide that I liked, but that is purely an opinion. Others prefer the glass slide to all others. I would venture a guess that a majority of slide guitarists use glass guitar slides. 

As you can see, the price of a glass slide is relatively low in comparison to a porcelain or metal slide. As I stated earlier, this is primarily due to the material cost of making the slide. They are also probably the most popular slide type, so the price is lower due to a larger supply. They are not inferior slides. I prefer the porcelain slides but that is entirely my opinion. I also, primarily play slide on my regular acoustic guitar. For a normal acoustic, glass or porcelain are both good choices. I probably wouldn't play electric slide guitar with a porcelain slide. They are much too heavy and would cause extensive fret noise, I suspect.