How to tell if the record is worn out?


Hi
On my recent trip to WFMU annual record show i encountered a problem that i've never dealt with before.Out of 50 records that i bought there 30 turned out to be worn out to a point where you can't even listen to them.Visually they look perfect though as if someone carefully played them from the beginnig to the end a 1000 times on a bad turntable,not a single scratch or fingerprint.I don't know if i's just a bad luck or since the show became annual instead of twice a year maybe many dealers do not care about returning customers any more?Is there any way to tell if a record is in bad condition?Maybe i should bring a big magnifying glass with me next time,the problem is:i don't know what to look for.Any opinions on this one?
overhang
I think Groove Glide is great - I use mine all the time to lubricate my table saw and band saw blade but I will never again put it on a record. Not that it does anything terrible immediately but I suspect any type of added material like this will attract and adhere more dust and dirt over time and many other posters have commented that it adds its own sonic signature to the music.

I cannot specifically implicate Groove Glide in the records I have had problems with which is why I said "Groove Glide or a similar type of product" in my post above. Obviously I don't know exactly what some previous owner might have applied. But it is apparent from microscopic investigation that some sort of dirt adhering gunk is in the grooves which is far more difficult to remove than normal. I should mention that I typically use a 4 step cleaning process for used records which involves 1) a basic distilled water / alcohol/detergent recipe like you can find anywhere on the web scrubbed on using Last applicators and rinsed under warm water in the sink and record vac'ed off. Then 2&3) Paul Frumkin's 2 part enzymatic and alcohol solutions. The I test play the record and if there is any residual surface noise, I use 4) RRL's Super Vinyl wash. This is all dome with a modified shop vac setup which does a very good job if not quite as pristine as I have experienced from something like Doug Deacon's Loricraft which can do it all in a single pass (but at much greater expense).
This will typically produce an LP where the stylus remains perfectly clean through playing the LP or might need slight touch-up (a repeat cleaning) if there is a little residual dirt picked up. On a few records, however, (and I can think of only 4 out of about 600 used jazz LP's I've purchased), The stylus will be completely gunked up with crap after just the first track, even after this cleaning. It is clear to me from this and the generally "duller" appearance of the LP, that something has been applied and it takes many additional playing and cleaning of these records to begin to remove the material. (One such record was an otherwise mint copy of Art Farmer's "Farmers Market" which has some tape / pressing noise even in a mint original which I suspect some former owner thought was groove damage they could remove with Groove Glide or similar product.)
you need to tote a portable record player with you.

http://www.needledoctor.com/Vestax-Handy-Trax?sc=2&category=43

You can hear enough with one of these to tell if the record is ok.

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I had put 300 LPs away 25 years ago. I recently purchased a turntable so I pulled then all out .They looked almost brand new. I cleaned all of the LPs manually with Disc Doctor. Every Lp I played was almost unlistenable but the ones I had just bought at a yard sale for $2 apiece sounded great. I thought that I must have ruined all my old albums with a worn out stylus or improper cleaning years ago. After cleaning all the LPs by hand I bought a VPI 16.5 and cleaned them all again using the same Disc Doctor solution. I almost fell out of my chair, all the LPs that I thought had been ruined played like new. So for me it is a combination of a VPI 16.5 RCM and disc Doctor. My guess the albums you think are worn out just might need the proper cleaning.