|
I would like to revive this thread, wherein, last spring, I put in my two cents worth about a less pricey solution to our flaking Aquadag. It's Slip-Plate, available in an aerosol can from any W.W. Grainger location.
In the last post from the end of May, Kirk suggested some resistance checks across the Slip-Plate coating. That seemed appropriate to me and now I've finally gotten around to it. This would be a bit of testing to see whether we can have confidence that the Slip-Plate is electrically suitable as a substitute for the Acheson Industry's Aquadag – which I believe is now a bit more pricey than Bailey's Irish Cream.
We know the Slip-Plate's color looks exactly the same as 'dag after application. It's adhesion and resistance to abrasion appears to be as good or better. 'Dag's carrier is water, Slip-Plate's is acetone, etc. Could it be that for the inside of a CRT, the water base is required? Could the water base be a poor choice for the outside? – but was mistakenly used at the factory – or that it was good enough for five years but not fifty.
The Slip-Plate's label says it’s "electrically conductive." But its web site does not put a number on that electrical conductivity. My online research didn't come up with any easy protocol for measuring that. I'm not a paint chemist – let alone a "coating applications engineer with NASA." Needless to say, I'm not a capacitor designer either. But let's not forget that we're dealing with glass bottles – not a space shuttle. Perhaps others can comment about the downside of trying to use a CRT with most of its 'dag missing. I do know that a peeling CRT is much less shabby with the smart new coat of graphite – pulverized pencil lead.
Anyway, I had a nice test surface – the funnel and face plate portion (all that was left, thank you UPS) of a 10BP4. I proceeded to knock off the big flakes. Methylene chloride paint solvent with some steel wool easily finished that job (of course, avoid skin contact or breathing the fumes). It was now clean as a whistle. I sprayed on a new coating of Slip-Plate. Nothing critical, just about the way you'd put some cheap spray paint on a kitchen chair. (When I do a working CRT, I do take the time to try to duplicate the factory masking of the neck, the anode area, and a couple inches back from the face plate.)
With no phosphor to protect, I did the major drying in the sun, with a little oven baking just to make sure all the solvent was driven out. For convenience, I used a little ancient digital auto-ranging RS multimeter to measure the resistances. (checked it against my big VTVM as a basic calibration check.)
I measured my fresh paint job against the existing good 'dag on various 10" and 12" roundies. Basically, the Slip-Plate was "in the middle of the ballpark." The range among what appeared to be factory coatings was about what you would expect from different factory setups where coating thickness is, perhaps, not that carefully controlled. There was expected variance depending on the separation between the probes. There was also variance in different locations (with same probe separation) on the same tube.
One of the CRT's I tested was a new 12KP4 (base has RCA "stencil font" logo) and its 'dag also tested right in the neighborhood – about the same as the Slip-Plate job.
My conclusion is that the Slip-Plate material is a good substitute for those of us who are on a budget – most of us – maybe all of us now.
I would welcome any comments about your own experience or your own musings – whether you are a NASA engineer or not.
Roger
|