Snap, Crackle, Pop - What is the cause?

First, I love vinyl. I would never say it is superior to digital but it truly sounds different. I am able to make an emotional connection to the music from an LP far more than from a CD.

That being said, I buy a lot of used vinyl at records shows, shops, etc because there really is so much available and for the most part, cheap too. The only thing that always intrigues me is the snap, crackle, pop on some records and not on others. Even they are the same title, label and pressing. Some of it is so bad,, it make an otherwise well recorded album unlistenable especially on soft passages in classical music.

So where does it come from? Is it static? Is it worn, damaged vinyl from being played on cheap and less than desirable cartridges from back in the day or is deeply ground in dust and dirt embedded in the grooves?

I clean all my recently purchased used vinyl with a Spin Clean system first and bag them in anti-static MoFi sleeves. I still get the Rice Crispies on some receords but not all. I buy and enjoy enough of it to consider investing in a better record cleaning machine like a VPI or Okki Nokki, but before I do I really want to know where the Rice Crispies on some records come from. If it is damage from being played on cheap equipment, no expensive machine will help. But if its dust and dirt, then maybe I should get an vacuum cleaning system and will take care of it? Your guidance is greatly appreciated.
if the vinyl is used it could be from the prior owner's old crappy cartridge that damaged the grooves during play.
some of the vinyls were touched right after or during munching a burger that shed grease over the fingers... yak(burp)
If it is caused by static, GruvGlide will quiet the noise. Whatever anyone might say about GG's effect on record wear or whatever, it absolutely stops static discharges. If you live in dry conditions where static is a problem, it's an excellent solution. Also, it lasts a long time - you do it once after you clean the record and you're done basically till the next cleaning. Others will tell you it's no good. Your choice.
Thanks everyone.

I have now had three replies and each one is different. One says worn vinyl from being played on crappy equipment. Another says dirts and grease. A thord leans towards static.

I would think this is an issue that matters to all of us who love vinyl so we should all be interested. So please keep the replies ciming - whats the cause of the Snap, Crackle and Pop on some records but not others. Thanks again!
I don't "lean towards static". I said that IF the noise is caused by static, GruvGlide will help. If it's caused by damaged grooves, it probably won't. There is no one cause of noisy records. If it bothers you that much, I would stick to Mint or Near Mint records. When you shop for the very cheap, you may well hit some stuff in excellent condition, but you have to be prepared for a lot of noisy records.
04-28-13: Paraneer
I have now had three replies and each one is different. One says worn vinyl from being played on crappy equipment. Another says dirts and grease. A thord leans towards static.... whats the cause of the Snap, Crackle and Pop on some records but not others.
All of the above, as well as several additional factors, some of which may not actually cause tics and pops, but may have a huge effect on how perceivable/objectionable they are. Additional factors include:

1)The profile of the stylus. And also how the profile of your stylus differs from the profile of the stylus that had been used to play the particular recordings previously.

2)The dynamic range of the music, as you appear to realize. Everything else being equal, tics and pops will be far more noticeable, for instance, during the soft passages of well recorded classical symphonic music, having wide dynamic range, than they will be on rock recordings that are often compressed such that they have very little difference in volume between the loudest and the softest notes.

3)The design of the phono stage.

4)The electrical loading of the cartridge.

5)The mechanical setup of the cartridge.

6)The pressing quality of the recording.

This thread, which touches on several of these factors, will be well worth reading in its entirety, IMO.

-- Al
Thanks everyone for the addituonal responses. Sounds like it may be a combination of all three factors I sited plus several more.

Chayro, while you may not lean toward "static", your answer did. You did not mention worn vinyl or embedded dirt like the other posters. Thats OK though, you may be right. I don't know - that why I am asking the question in an attempt to understand what causes it. Then I can more effectively combat it.

Can't say it bothers that me much - At a buck apiece, I can buy many copies of the same title in hopes of getting a clean one. And throw or give away the rest. I also buy new wherever possible if its a title I like in hopes of getting a real good one. Even new pressings are no guarantee.

As mentioned earlier, I visually inspect the used record before buying, run it through a Spin Clean machine and then bag them in MoFi sleeves. I am wondering if I should invest in better vaccuum machine and if this will help removes the noise? If not, might as well keep buying multiple used copies and hope for the best.

I believe a lot of problems are in the processing of the record. Flaws in the vinyl.
My setup is remarkably quiet, even though I rarely clean my records. I find that my old records many times sound better than recent purchases. ..just thinking of the new Paul Simon LP, and the new Norah Jones LP...both have good music, but recorded poorly.
The Spin Clean does a good job of scrubbing a record, but unless you follow with a vacuum, a portion of the gunk will remain on the record. I use the Spin Clean followed with the $169 KAB EV-1, which is a Nitty Gritty without the built-in vacuum. Use a regular vacuum cleaner for suction.
Any of the above-mentioned causes may contribute to snaps, crackles & pops (although static is rarely involved, in my experience).

I listen primarily to classical, including thousands of authentic instrument and early music LP's, and 95% of my records are dead silent. I've addressed these issues and rarely experience more than an occasional "click".

As Almarg stated, the quality of the stylus and phono stage can make a huge difference. Better designs are much quieter, but may also be costly. That upgrade path is not for everyone and not something to be done quickly.

Aside from equipment, in my experience the single most effective step for reducing/eliminating SnapCracklePops is proper cleaning with an enzyme-based solution. After testing many I found Audio Intelligent Vinyl Solutions to be the most effective. MoFi's solution also worked pretty well. Haven't tried the Walker solutions but they have adherents among people whose ears I trust.

Whichever solutions you use, vacuum removal is necessary for optimal results. Cleaning solutions dissolve grunge that's in the grooves, that's their purpose. Spinning won't remove grunge-saturated liquid from deep down in the groove bottoms. If you let residues evaporate what happens to the grunge? It's right back where it started, except you've broken it down into finer particles that may be even harder to remove.

Suggestion: try AIVS's One Step. It includes their enzyme mix and won't cost much. The results will quickly tell you whether this is a process you want to get into. Your Spin Clean is good enough for now. If you decide to get serious then a RCM will be an item to budget for.
Thanks again to everyone for your thoughful and intelligent responses. I posted the same question on vinylengine and the replies are similar - a good vaccuum record cleaning machine will help the situation along with careful selection of cartridge/stylus and preamp.

For the record I running a Sumiko Blue Point No. 2 along with a Pro-ject Phono Box S that allows for precise loading. I really like this combo, especially the preamp vs. others I have tried, and feel I have the cartridge dialed in pretty good. So it seems there will be a RCM in my future. Looking at the VPI 16.5 or Okki Nokki as both are in my budget. Anything else I should be checking out?