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Finishing Q's: Re: High-Heat Automotive Paints....

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  • MSaturn
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    I have neither the software nor the patience (or money) to worry about micrometers in products I do not have the time to test in a controlled environment before I sell them. And yes, it is a small concern, but it's the only one I can think of when we're talking about perfectionist paints and cabinets in this context.

    Leave a comment:


  • r-carpenter
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Better engineered speaker cabinets or any other cabinets will have joints that are either designed properly or the expansion and contraction of the MDF (plywood) becomes a design element. Not removing drivers from the speaker has little to do with why and how the cabinetwork either lasts or perishes. Early Sonus Faber speakers made with the stave of solid maple were know to split and crack. Some of the low end to mid-range Italian furniture finished with variety of backed on polyester coatings also suffered from this symptoms, especially then panels were butted and glued.

    In addition to what Bob said about blushing.
    Having a fast evaporating solvent usually means, the finish with start curing very fast, and the amount of dust caught would be minimized. Problem is then the solvent evaporates, it cools off the surface of the paint and the moisture settles on it, creating the milky film effect. So, it's a catch 22.

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  • MSaturn
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Whenever I've done high-sensitivity paint jobs with serious piano-lacquer (and not just the faux variety) finishes, I use a climate-controlled shop with low humidity and an adjustable "baking" setup using lamps or heating units to dry the material after finishing construction ... aka once the raw piece is done, I let it sit at unnaturally high temperatures like 125 degrees until it's totally dried out so the joints can move if they like, and then it can be sanded, filled and sealed. Bake it once more at a low temperature and look for movement, then do the final sanding and sealing. Then on go the basecoats and waiting .. then the final, volatile lacquer that has to be baked at higher temperatures. Has always worked for me, and it prevents joints showing up due to age. You could do something like this with little more than a dehumidifier and some lamps. For those who are worrying about the MDF picking up moisture again - well, people who buy seriously-finished speakers usually do not remove drivers or mess with anything.

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  • bobbarkto
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Good one! Nice escape!

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  • marvin
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Originally posted by bobbarkto View Post
    Heh!
    Yeah, more and more of us wind.. Windy City folks around here. Good for us!
    Cubs or Sox, or don't care?
    Your answer will be very telling to Chicagoans....:rolleyes:
    I spend little time watching sports.....too interested in speakers and forums:p

    I live south, but work all over Chicagoland.

    Leave a comment:


  • winslow
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    If it's going to be hot, stick them in your car while it is parked in the sun...it won't be 200 degrees in there, but will be hot. Hotter than sitting outside.

    Leave a comment:


  • bobbarkto
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Heh!
    Yeah, more and more of us wind.. Windy City folks around here. Good for us!
    Cubs or Sox, or don't care?
    Your answer will be very telling to Chicagoans....:rolleyes:

    Leave a comment:


  • marvin
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Originally posted by bobbarkto View Post
    Blushing is most often a problem with lacquers, which were very common in auto repair shops until fairly recently. The solvents used and the quick drying nature combine to cause this "blushing". Shellac is much the same.
    Modern urethanes are much less sensitive but are not immune.
    Enamels are largely immune due to the different solvents and the slower drying.
    There are formulations that cross boundaries and might seem to be less trouble but can still blush.

    Yes, to some extent, canned spray paint is somewhat less trouble because the air in the can is very dry. But once the paint leaves the can the solvents will suck water from the air and substrate.
    Air compressors can introduce huge amounts of moisture, and if not removed it poses all sorts of problems.
    Good info, Bob. We sure enjoy a broad panel of experts on this forum! And you're local, too

    Leave a comment:


  • bobbarkto
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Blushing is most often a problem with lacquers, which were very common in auto repair shops until fairly recently. The solvents used and the quick drying nature combine to cause this "blushing". Shellac is much the same.
    Modern urethanes are much less sensitive but are not immune.
    Enamels are largely immune due to the different solvents and the slower drying.
    There are formulations that cross boundaries and might seem to be less trouble but can still blush.

    Yes, to some extent, canned spray paint is somewhat less trouble because the air in the can is very dry. But once the paint leaves the can the solvents will suck water from the air and substrate.
    Air compressors can introduce huge amounts of moisture, and if not removed it poses all sorts of problems.

    Originally posted by marvin View Post
    Way back when I worked at a car dealer the body shop tech would not spray paint anything on very humid days because it would "blush" --have a milky white film in or on the color. Maybe it is more of a problem with air compressor paint methods than rattle cans where dry air is compressed at the factory.

    Leave a comment:


  • UGP
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Originally posted by tomzarbo View Post
    Ben,

    My front door at my house faces the sun and I have a large full glass storm door on the outside. When I open my door it is so stinking hot in that little cavity that I can hardly touch the door to open or close it.

    I think it would be possible to get a scrap of glass (from an old storm window, etc. and build a little box out of junky old plywood and paint it dark inside and out. Have the glass side facing the sun and let it bake for the hot part of a few days. I've thought about doing this several times, and may end up using the halogen bulb "heater" trick to cure the MDF in my current project.

    I would think this would work pretty well for curing paint. I'd be awful nervous about having something wood in an oven. I once tried to bake a finish on a metal piece I made in our electric oven, and even on it's lowest setting, the paint got funny in a few areas. I would hate to see your beautiful speakers have a goofed up finish on them after all your hard work.

    TomZ
    that's just what I was thinking yesterday (though for a different material that needs "baking") my Dad drove truck for a little while in the late 80's and delivered the "Sun Oven" http://www.sunoven.com/ he bought one and we all though "that's not going to work" but it's the best food ever, easily gets up to over 350 deg. so a box with some plexi will get very warn/hot

    Leave a comment:


  • marvin
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Originally posted by Wolf View Post
    I really don't know what blushing is as I've not had much trouble. Occasionally I get orange peel if I recoat too soon or use incompatible paints/finishes, but If I apply on a cooler less humid day and then it sits in the hot garage and bakes on hotter more humid days I usually don't have problems. Sealing the material on a day that is also better for paint can also make applying in slightly higher humidity acceptable as the moisture is not in the material and also not in contact with the applied paint.

    Funny thing about what I'm working on...

    Since I used hardboard and applied a coat of glue and then sanded it when dried, I had already sealed the material. I did not have to apply primer on the Glue applied surfaces. It still looks fantastic like I had used primer.

    Later,
    Wolf
    Way back when I worked at a car dealer the body shop tech would not spray paint anything on very humid days because it would "blush" --have a milky white film in or on the color. Maybe it is more of a problem with air compressor paint methods than rattle cans where dry air is compressed at the factory.

    Leave a comment:


  • Wolf
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Originally posted by marvin View Post
    I'd be interested to see a 1,000 watt fluorescent lamp...I've never heard of that.

    Also, doesn't spray paint tend to "blush" when applied under too much humidity?
    I really don't know what blushing is as I've not had much trouble. Occasionally I get orange peel if I recoat too soon or use incompatible paints/finishes, but If I apply on a cooler less humid day and then it sits in the hot garage and bakes on hotter more humid days I usually don't have problems. Sealing the material on a day that is also better for paint can also make applying in slightly higher humidity acceptable as the moisture is not in the material and also not in contact with the applied paint.

    Funny thing about what I'm working on...

    Since I used hardboard and applied a coat of glue and then sanded it when dried, I had already sealed the material. I did not have to apply primer on the Glue applied surfaces. It still looks fantastic like I had used primer.

    Later,
    Wolf

    Leave a comment:


  • marvin
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Originally posted by Wolf View Post
    I just finished laying out some paint on a project with VHT High-Heat Burnt Copper, and went to look at the label (I know- shoulda read it FIRST!), and it said for best results to bake at 200* for 1 hour.

    I would obviously remove the xover, all wiring, drivers, and stuffing before attempting this.

    Now I'm contemplating doing it to get the full cure and hardness of the paint for durability's sake. I've just been looking up items on-line to see if they can tolerate the heat:

    Adhesives:
    Elmer's Glue-All
    Gorilla Glue

    Media:
    MDF
    1/2" thick cardboard tubing
    1/4" Hardboard
    Particle Board/Formica
    Biscuits
    Screws
    Clay kitty litter

    Paints currently on the cab:
    Krylon variety enamels testing for color, small spots
    Krylon Flat Chalkboard Black
    Krylon Matte finish
    VHT High-Heat Burnt Copper

    Now- I remember Aaron Hero used to 'bake' his boxes via a 1000W fluorescent bulb and a couple fans piping the heat through the inside of the enclosure to prevent seams and cure the glues, etc. (Not OSHA approved, but it worked under watchful eye!)

    Do I have anything I need to be concerned about in the cabs as they are currently containing the above items if I were to bake the cabs?
    Thanks for any insight any of you can offer,
    Wolf
    I'd be interested to see a 1,000 watt fluorescent lamp...I've never heard of that.

    Also, doesn't spray paint tend to "blush" when applied under too much humidity?

    Leave a comment:


  • Wolf
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    Originally posted by bobbarkto View Post
    How fresh is the paint?
    How many layers, dry time between (including primers and sealers)?

    Any excessive heat has the potential to cause problems if the paint isn't dry or on damp substrates. Ever see old house paint blister in the sun? That little greenhouse could hit close to 200 if it's not well ventilated. Mid 100's with only slight ventilation.

    Take care...
    Either way- I'm waiting a week before I attempt to sand or recoat. If it cures fine by then for the most part, then I won't feel the need to sun-bathe the cabs. I was not entertaining the greenhouse idea for this either way, just that it was an interesting thought prospect.

    Thanks, Bob!
    Wolf

    Leave a comment:


  • tomzarbo
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    How'd my post get here an hour later?


    Ben,

    My front door at my house faces the sun and I have a large full glass storm door on the outside. When I open my door it is so stinking hot in that little cavity that I can hardly touch the door to open or close it.

    I think it would be possible to get a scrap of glass (from an old storm window, etc. and build a little box out of junky old plywood and paint it dark inside and out. Have the glass side facing the sun and let it bake for the hot part of a few days. I've thought about doing this several times, and may end up using the halogen bulb "heater" trick to cure the MDF in my current project.

    I would think this would work pretty well for curing paint. I'd be awful nervous about having something wood in an oven. I once tried to bake a finish on a metal piece I made in our electric oven, and even on it's lowest setting, the paint got funny in a few areas. I would hate to see your beautiful speakers have a goofed up finish on them after all your hard work.

    TomZ
    Last edited by tomzarbo; 06-17-2014, 06:39 AM. Reason: Some Fantastical, Magical, Radical Self-Posting Cyber-Mystical Weirdness Goin' On

    Leave a comment:

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