Coefficient of friction, ratio of the frictional force resisting the motion of two surfaces in contact to the normal force pressing the two surfaces together.
Q.Yeah, okay smarty pants. But what the heck are you talking about?
A. Hey, don't blame me, blame Newton. Put simply, what effect certain materials have when moving across the surface of each other. In this case a record and substrates used to make inner sleeves.
I think we have all heard different opinions from many different people about which inner sleeve is the best? Have you ever asked yourself how they have come to that conclusion? Do they have any scientific facts to backup their claim?
Would you believe that all inner sleeves are generally fine for storage and the real reason that your records develop hairline scratches may be because of you or the record itself? I know, "that's fighting words" Mike!
If you look at a great report published by The Vinyl Factory you'll see that our precious records are jagged, maybe have slighted barbs (from manufacturing, ever have the one record where the edge is rough and jagged?) and ridges. They are great at slowly cutting into the substrate on the inner sleeve, if the right amount of pressure is applied. This pressure can be from having many records stacked against each other. This intern creates dust and barbs in that material. Always try to leave a little space between records when in storage.
In reality there are two significant actions that help to produce hairline scratches, 1. pressure and 2. movement.
- Have you ever opened a new record that already had scratches, regardless of the inner sleeve? Some people call this a "rash".
- Have you ever accidentally dragged the record over another surface?
So the COF applies an equal amount of pressure and movement. Each sample is tested under the same conditions to determine the effects of pressure and movement on the record, thereby allowing you to understand what the long term effects maybe.
Substrates tested at an independent certified lab in the USA.
1. VSS HDPE. Standard 2 mil rice paper inner sleeve.
2. VSS crystal clear inner sleeve (prior to 12/3/21)
3. Poly fibre inner sleeve
4. Paper/Poly inner sleeve
5. Paper. Standard record sleeve.
6. VSS crystal clear inner sleeve (from 09/20/22)
Note: no bias or defamation intended or implied on any product tested.
I sacrificed 10 Kenny Roger's albums to this test. All new and sealed. All from the same pressing company. Sorry, Kenny, but I "lost that lovin' feeling" for these records!
The higher the value indicates a "rough" surface interacting with the already rough surface of the record. A lower value is preferable, but not necessarily required, just maybe avoid storing the bare naked record in the cardboard jacket!
COF < 0.25 is considered LOW COP & HIGH SLIP
COF > 0.45 indicates HIGH COF & LOW SLIP
Testing was performed in accordance with ASTM D1894.
Test Conditions and Parameters
The following parameters were used:
Speed (mm/min) 150
Traveled distance (mm) 50
Material - Sled Sleeve
Material - Plane Vinyl
Weight – Sled+Sample (g)
198.7 to 201.1
Cleaning - Sled None
Cleaning - Plane None
Relative humidity 45-48%
|item||static μs||kinetic μs|
Test conclusions? Other than HDPE having a slight lower COF, all products are basically the same when it comes to interfacing with a vinyl record. Most dry materials in combination have friction coefficient values between 0.3 and 0.6. So don't take these numbers as absolute!
Reality Check! We as vinyl collectors just need to be careful not to drag a record across any material. Like pulling a record out of a jacket, that is tightly sandwiched between other records. I'm sure we have seen people do that!
Let's not forget that items 4 and 5 generate paper dust, by their COF from sliding the albums in and out of the jacket. The best way to avoid that situation, use my dual pocket outer sleeves! A little shameless self promotion.
So hopefully the science will speak for itself and you'll find this info useful regarding the handling and storage of the "imperfect" media. And always use an inner sleeve, any inner sleeve is better than nothing.
I want to thank everyone that has supported me in this business venture, passion and hobby. After almost 30 years in the manufacturing field, be it in plastics, metals, print or food, I can honestly say that there's a heck of a lot truth to the saying "do what you love and you'll never work a day in your life"!
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