#diamond discs

[dinosaurdiscs]

Diamond Disc recording lathe.

[con-treat]

How to use polished concrete equipment

Standard Procedure:

This is a GUIDE to the normal procedure involved in polishing concrete, including exposed aggregate concrete surfaces and using Polished Concrete Tools. The procedure is virtually the same with terrazzo, and other natural stone products. Note that this is quite different to creating a polish effect by grinding and then coating concrete floors with a clear coating such as epoxy or polyurethane, these use the coating to produce the sheen. Firstly, a very important word: - no two slabs are the same, even on the one job, so talk to the experts before you buy polished concrete equipment!

 Therefore you:

# Cannot predict what the slab will look like - whether the aggregate is going to be evenly exposed; or patchy, because the contractor who placed the concrete pushed it down with his boots. The great thing you can tell the customer before you quote the job is that “your slab will be totally unique to you.”

 # cannot predict how much topping will need to be ground off to expose the aggregate.

 # Cannot always predict how hard the concrete will be to grind. Use polished concrete equipment to complete a test patch before you quote to give you some idea both on how hard and how much may need to come off. How readily the surface will take on the required sheen. This can change dramatically depending on how porous the slab is due to water being added to the mix when pouring or air bubbles from not being vibrated.

 Typical Procedure:

1. The FIRST CUT is the grinding of the required amount off the top to expose the aggregate; some want ‘salt and pepper’ with the aggregate partially exposed, or the customer may prefer a heavy exposure. The first cut done with polished concrete tools is always completed in several passes and at an even speed so no part of the floor is over ground and forms an ‘ocean wave’. The first cut is done with coarse production grinding disc or tooling, 30-60mesh is common; 25 and 16mesh also is used to do the first part of the first cut. In practice the amount that is removed is often 2- 3mm and is removed in .5mm per pass. This means that if 3mm is removed, this will be done in 6 even passes to ensure flatness. So to quote a six pass floor properly, you need to quote on grinding 6 times the floor area. A shot blaster in the hands a skilled operator can drastically reduce both the cost and time to get just the top off the slab; especially if the slab is highly toweled (burnished).

 2. SECOND CUT: Following the first cut it is best to do a finer grind with 60-80 mesh Diamond Discs to remove the all score marks from the coarser discs before you move the final metal bond cut.

 3. THIRD CUT: Following the second cut it is best to do one thorough fine grind with 120-150mesh diamond discs to remove the all score marks from the previous cut before you move into the polishing process. The important point here is that the phenolic polishing pads are not intended to remove score marks and wear fast on a coarse ground surface. Guide to quoting: So far in this example you have taken 8 even passes to do the job. If you charge at $8 per m2 for a single pass grind, this job is 8 passes x $8 per sq m = $64:00m2 for this stage.

[sidewalkcritic]

Issue 47 of Record Research magazine. California Ramblers, Mildred Bailey, electrical reproduction of vertical-cut (hill and dale) records, Georgia Minstrels,...

[vinylspinning]

Glen Ellison: "A Wee Deoch and Doris" / "Doughie the Baker  (It's Nicer When You Make It Up Again)" (1917)

Is this history's first Betamax (i.e. a failed entertainment media delivery format)?

Until I saw a stack of these things in a Half-Price Books store I'd never even heard of Thomas Edison's 10-inch-across, 1/4-inch-thick, 80 RPM Disc Records, which were seemingly incompatible with common phonographs of the era, and required a diamond stylus, to boot.

So, like other exclusionary music formats that followed, Diamond Discs, as they were called, enjoyed a limited existence (between 1912 and '29, and I'm surprised it was that long!) before vanishing, along with much of the music they carried.

So much so that I had to track down this ultra-nerdy collector's site to get a proper listen of Scottish folk singer Glen Ellison, since my modern record player can't play the darn disc -- wrong speed, wrong stylus, etc.

Even worse, I shouldn't have bothered, because it seems that Thomas Edison himself was acting like some prehistoric A&R man and deeming what artists and songs were "worthy" for recording on his pet format...and his music taste was pretty lousy.

In other words:  I won't be collecting too many of these unplayable things moving forward.

More Early 20th Century Music: Georgia Tom, Son House, Skip James, Blind Lemon Jefferson, Robert Johnson, Tommy Johnson, Lonnie Johnson & Victoria Spivey, Meade Lux Lewis, Duke Ellington, Charley Patton, Bessie Smith, Fats Waller, Ethel Waters, Alexis Zoumbas.