If a question is not a chemical, can a chemical be a question?

[thechemist]

I seem to have been uploaded again, and here is a new cyberspace.

Hello, one and all.

Are there any technical questions that need to be addressed?

[Scott Rosen]

Technical questions? Yes. How the heck are you?! Welcome back. You've been sorely missed.

[thechemist]

How?

Beats me.

I just am, is all I can tell.

Hope you are not too sore.....the absence was unavoidable, albeit of greater duration than expected.

What's the question?

[NormMessinger]

Welcome back. I hope the cause of the absense was pleasant.

There was a question as to whether or not we are just a mass of electro-chemical reactions controled by a random agrigation of a few simple protiens a while back but we shouldn't get that going again. Can't remember the question but there was one a while back that sorely needed your expertise. No doubt it will resurface.

Best.

--Norm

[Ed Nye]

Glad to see (read) your back. Your totally logical approach to most matters has always been of great interest to me.

Paint question - What makes an oil based paint hard or soft? Is there a low gloss hard paint? Car paints are hard. Marine paint is supposed to be hard. House paint not so hard. And, what is a reasonal time for a paint to get hard?
Welcome back,
Ed

[gert]

Welcome back

[TomRobb]

Welcome back! smile.gif

[imported_Conrad]

Ah, very cool- hope all is well, glad you're back!!

[John B]

Well? come on. what did happen when you approached lightspeed? shorter and fatter or not ;) ?

[Rich VanValkenburg]

Good to see you're back. There have been many times, voices crying out, 'If chemist were here....'

Rich

[thechemist]

Originally posted by Ed Nye:
Glad to see (read) your back. Your totally logical approach to most matters has always been of great interest to me. Thanks, Ed. It has always been of interest to me, too.

But, then, that would be logical.

That probably explains it.


Paint question - What makes an oil based paint hard or soft? Is there a low gloss hard paint? Car paints are hard. Marine paint is supposed to be hard. House paint not so hard. And, what is a reasonal time for a paint to get hard?
Welcome back,
Ed Well.

Let me say this about that.

Oil based paints may be hard or soft depending on the density of cross-linking and the amount of prepolymerized oilseed goo that is mixed in with the oilseed resins themselves. It may also depend in the stiffness of the molecular chains that are added to the mixture of varyingly prepolymerized goo. Those are alkyd resins of varying types, varying lengths and stiffnesses.....another sort of goo. Put 'em together and what have you got? slippetty glippetty glibbery gloppety goo. Welcome to the domain of the paint chemist. I'll bet you thought it was all fancy laboratories and people in lab coats carrying clipboards around and noting readings on big stainless tanks and pipes and gauges and stuff, didncha? A lot of that goo is in drips on the floor and gets tracked around.....and then the sawdust sticks unless someone throws kitty-litter on it first.

Low-gloss or high-gloss has absolutely nothing to do with hard or soft, until you get to certain points in the formulation.

Hard or soft has to do with molecules that are short and fat or long and skinny, and how many attachment points one molecule may have for others. Gloss has to do with surface roughness....how much of it there is and whether the roughness is much more or less that a wavelength of light, which in rough numbers is a few ten-millionths of a meter.

The way we get a flat surface, or satin, semigloss, etc., is to mix little microscopic rocks in with the paint or varnish. When the solvents evaporate the paint shrinks back in between the microscopic rocks, making a microscopically rough surface. The incident light scatters in all directions, not giving a coherent reflection. Thus, an image does not get reflected as an image, and one hath not gloss.

Now we get to where these overlap. If you take a flexible resin and mix rocks with it you get a harder cured result.

Flat or satin, etc., finishes are inherently less flexible than their otherwise identically formulated gloss versions.

Since a finish is normally two to twenty mils thick, and the surface roughness for an off-gloss appearance may only be some tens of microinches, it follows that one obtains the best of both worlds, and a far more durable finish, by putting on a full-gloss finish to build up the desired total film thickness, and then adding one off-gloss coat to get the desired appearance.

House paints, latices, are usually formulated for the most competitive consumer market, and latex manufacturers normally add as much little rocks as they can....cheap minerals such as talc....to simply make more volume at less cost to improve their margins. It's nothing personal. It's just business.

Car paints nowadays are apparently hard because they are on metal, but under a microscope those two-component polyurethanes [color-coat/clear-coat] are pretty flexible. they also seem hard because they do not scratch easily, but that actually is due to the mixture of molecules of different sizes, which is what gives polyurethanes [the good ones] their incredible tear resistance, and thus, microscopically, great scratch resistance...ability to survive sandstorms and so forth.

Marine paint ain't necessarily hard. On wood, one must have a more flexible [often confused with soft] coating. The 2-part isocyanate-cured polyurethanes on aluminum masts can survive abuse by wind-whipped lines far better than a rockhard epoxy coating of the same thickness, although some polyurethanes are a LOT better than others. What's sold for aircraft ain't necessarily what you buy at a marine store or Brand X mail-order.

The time it takes anything to get hard [if ever] depends on so many things that I cannot give you a pat answer.

For paint curing ["getting hard"] try using the search thingy in Building/Repair for the word LEAD in the body of the post. You should find, thereby, several times I have gone into drying of varnish [same technology as oil-base paints].

As for latex paints getting hard, that depends on the humidity and temperature. If the conditions are too cold and/or humid, the water does not evaporate soon enough before the coalescing solvent, [and if the stuff was not formulated right there's no hope at all, and believe me latex paint producers DO screw up] or the coalescing solvent may leave too soon or not, and then the stuff never gets hard and weathers a lot faster.

For two-component paints getting hard, mixing incompletely or wrong-ratio can similarly doom the job, and then the answer is never.

So, there you are.

And here I am.

And there's the show.

[thechemist]

Originally posted by John B:
Well? come on. what did happen when you approached lightspeed? shorter and fatter or not ;) ?Of course.

There once was a fencer named Fiske,

whose fencing was agile and brisk.

So fast was his action,

the Fitzgerald contraction

reduced his sword to a disc.

[Andrew Craig-Bennett]

A mosquito was heard to complain

That a CHEMIST had poisoned his brain

The cause of his sorrow

Was phenyl di-chloro

Di-ethyl tri-methyl ethane!

[ 06-19-2002, 03:32 AM: Message edited by: Andrew Craig-Bennett ]

[G. Schollmeier]

It's nice to see that userid again. :D
Gary

[Scott Rosen]

ROTFLMAO!

The British are still the masters of the language.

[norske2]

The British...the British.....interesting word...does anyone know what it means?

[JimJ]

I know where thechemist has been. He was the subject of a teleportation experiment down in OZ.


ABC News - Scientists conquer laser beam teleportation Star Trek, but a team of researchers from the Australian National University (ANU) has carried out a successful teleportation experiment in a gravitational wave lab. AEST Scientists conquer laser beam teleportation. Scientists in Canberra have successfully teleported a laser beam for the first ... experiment in a gravitational wave lab. Team leader Dr Ping Koy Lam says it involved creating a laser beam, its disembodiment and the recreation of the original beam in a different location.
http://www.abc.net.au/news/australia/act/metact-17jun2002-1.htm

The secret is out!

thechemist is a laser beam.

[imported_Steven Bauer]

Here's a question: can I prime bare cedar with CPES when there is 3-m 5200 nearby? The gains at the ends of the planks are bedded with 5200. I know that the tube of 5200 says not to use "some teak oils" as they can affect the 5200. I was going to skip the CPES because it's solvents seem pretty strong. I mixed some up in a plastic drinking cup once and it melted the cup and ran out on the floor. :(
Steven

[ken mcclure]

Welcome back, Chemist. You've been missed.

Seems to me that someone did a teleportation experiment awhile back and it worked. We had a small discussion about it here, if memory serves.

Unfortunately, the news about it was eclipsed by a story about Heinz coming out with a green ketchup, or some such. So much for science in the news.

The reason no aliens have contacted us is that they've concluded that there is no intelligent life here.

[Andrew Craig-Bennett]

Small, elegantly written graffiti, seen decades ago on the wall of the Cavendish Laboratory, Cambridge:

"Is there intelligent life on Earth?"

and underneath in a smaller hand, using gren ink:

"Yes, but I'm only visiting" !

[TomRobb]

Norske2,
Brittish: caned regularly at cold damp public school, classics heavy education at Oxbridge, regimantal tie, inexplicable need for tea, can't understand why everyone doesn't keep horses at their country estates.
Gentlemen, Long live the Queen.

[ 06-19-2002, 08:20 AM: Message edited by: TomRobb ]

[thechemist]

Originally posted by Steven.Bauer:
Here's a question: can I prime bare cedar with CPES when there is 3-m 5200 nearby? The gains at the ends of the planks are bedded with 5200. I know that the tube of 5200 says not to use "some teak oils" as they can affect the 5200. I was going to skip the CPES because it's solvents seem pretty strong. I mixed some up in a plastic drinking cup once and it melted the cup and ran out on the floor. :(
StevenMost common solvents will melt strofoam, or even the clear molded polystyrene or butyrate plastic cups. Polyethylene and polypropylene are reasonably resistant to most strong solvents.

If the 5200 is REALLY well-stuck to the cedar, a brief exposure to most common solvent-blended products will not likely lift it. Why not try it on a bit of 5200 shaved off of the main mass with a razor blade? Soak it in a bit of mixed CPES and see if the rubber swells and wrinkles rapidly. If not, it should likely be safe to use the product near it. If that use causes the 5200 to lift off the wood, then I'd say the 5200 was not really stuck that well in the first place.

"some teak oils" are powerful paint strippers and attack most things. Use caution when using such products, testing first by soaking a sample of the wood/caulk combination in the stuff. Many caulks do not hold up to those things.

[Ed Harrow]

There once was a chemist so bright
That he travelled much faster than light
He left home one day, in a relative way,
And returned the previous night.

Now, that being true, how do we explain this apparent lengthy absence...

[ 06-20-2002, 09:40 AM: Message edited by: Ed Harrow ]