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

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

    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...

    Originally posted by Wolf View Post
    Well- It's supposed to be 92* tomorrow, and that is not as hot as inside the garage will be. I'll be letting them cure all week in the garage, and see if I still then need to sun-cure them. This is how I normally do it, so I should be okay. You pretty much conveyed my sentiments exactly.

    A little green-house box, eh? Interesting....
    Wolf

    Leave a comment:


  • Wolf
    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
    Well- It's supposed to be 92* tomorrow, and that is not as hot as inside the garage will be. I'll be letting them cure all week in the garage, and see if I still then need to sun-cure them. This is how I normally do it, so I should be okay. You pretty much conveyed my sentiments exactly.

    A little green-house box, eh? Interesting....
    Wolf

    Leave a comment:


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

    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

    Leave a comment:


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

    Originally posted by greywarden View Post
    No that'd be the Gold engine block paint, I see them every day at work.
    I'm mainly worried about the paint flaking off, but time will tell. If applied on a sealed wood, the color is like the burnt copper on the cap. If applied on a porous surface, it yields a very rosy color, not unlike the color on the upper-end trombone's bells. Very pretty, and a NICE contrast from one color of paint.

    Again- thanks, all! I guess I'll just use UV and time,
    Wolf

    Leave a comment:


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

    Originally posted by bobbarkto View Post
    Elmers PVA glue has pretty low heat resistance.
    It starts to soften at 85F.
    If the glue line is stressed it will deform or let go.
    That's mainly what I was afraid of. The Elmer's glue being the weak link. Looks like the oven is out this go around.

    Make sure everything is really dry before you heat. Escaping moisture vapor and solvents can damage the finish.
    Noted for future reference.

    Aaron heated the bare mdf cabs to get the glue lines really dry before finishing. His temps never got that high. You only need about 10 above ambient to drive off moisture.
    Noted.

    Metal and wood behave differently. Metal won't absorb moisture or solvents so there is no worry about them popping the finish when heated. Wood products are more like sponges and it can take a very long time for excess solvents and moisture to evaporate to a point where it won't be a problem.
    Yep.

    Formica is also a thermoplastic. It will soften at 200F. How is it bonded? Is it stressed?
    It's not visible from the outside of the cab. I used the formica-particle-board discs from some cutouts to give a couple screws something to bite into, and it is in turn screwed to the cab. Far as I know it came from a cabinetry shop as sink cutouts, and was likely done by a furniture grade adhesive for kitchen countertops, or maybe just regular smelly contact cement. I really can't say as I purchased them bonded.

    Forgot to add.
    Bring it up to heat very slowly. Don't plop the cabs in the hot oven. Pre-heat the oven a little above room temp to drive off moisture, then put the cabs in. You'll have to manually cycle the heat to bring it slowly up to temp.
    Wow- I would not have guessed that to be operation practice. That is very helpful should I ever undertake the cure via oven. Thank you for the detailed reply.
    Looks like I might just set it in the sun for a bit as others suggested.

    Thanks all,
    Wolf

    Leave a comment:


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

    Originally posted by r-carpenter View Post
    the joints are very likely to show up. Did you **** join the cabs or miter folded?
    On the face of the cab, there are only 2 adjoining seams. The roundover could shift a bit, and there is one in the middle of that.
    I covered all else with a layer of hardboard and flush-trimmed, so I eliminated a ton of the bu++-seams. These are the PE Knockdown 0.23ft^3 cabs, altered, mass-loaded, and improved.

    Thanks,
    Wolf

    Leave a comment:


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

    No that'd be the Gold engine block paint, I see them every day at work.

    Leave a comment:


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

    Which VHT did you use? Is it the 1500 F header paint?

    Leave a comment:


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

    Elmers PVA glue has pretty low heat resistance.
    It starts to soften at 85F.
    If the glue line is stressed it will deform or let go.

    Make sure everything is really dry before you heat. Escaping moisture vapor and solvents can damage the finish.

    Aaron heated the bare mdf cabs to get the glue lines really dry before finishing. His temps never got that high. You only need about 10 above ambient to drive of moisture.

    Metal and wood behave differently. Metal won't absorb moisture or solvents so there is no worry about them popping the finish when heated. Wood products are more like sponges and it can take a very long time for excess solvents and moisture to evaporate to a point where it won't be a problem.

    Formica is also a thermoplastic. It will soften at 200F. How is it bonded? Is it stressed?

    Forgot to add.
    Bring it up to heat very slowly. Don't plop the cabs in the hot oven. Pre-heat the oven a little above room temp to drive off moisture, then put the cabs in. You'll have to manually cycle the heat to bring it slowly up to temp.
    Last edited by bobbarkto; 06-16-2014, 11:38 AM. Reason: additional comment

    Leave a comment:


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

    the joints are very likely to show up. Did you **** join the cabs or miter folded?

    Leave a comment:


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

    So- No one sees any problem with baking it though, correct?

    I talked with Matt on the phone last night about it, since he's done some car-parts this way which were metal. He says the finish not only reportedly gets more chemical resistant, but it also gets harder and more durable as a result.

    The paint looks just as I want it to, but I want the full adhesion and durability. Being that every day this week is supposed to be muggy, stormy, and hot; I'm thinking it couldn't hurt.

    So, really- I can do this, right?

    Later,
    Wolf

    BTW- I DO have an extra oven from when we changed ours last year, sitting stored in the barn. I was going to just give it away, but maybe I'll keep it on the 220 in the garage for things such as this.

    Leave a comment:


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

    my understanding of the bake process on that product is for it to reach it's full chemical resistance (think gas tank on a motorcycle)

    unless you're planning on subjecting your cab to some crazy environment, you should be fine with a normal cure and/or the backyard bake (which IMO is more about the UV rays than the heat)

    I used the VHT Copper on a tube amp chassis some time ago (it gets hot)...holds up fine. I never baked it.

    Leave a comment:


  • isaeagle4031
    replied
    Re: Finishing Q's: Re: High-Heat Automotive Paints....

    We're in northern Indiana. Chances of that lately seem to be slim to none lol

    Leave a comment:


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

    Originally posted by billfitzmaurice View Post
    'Bake' it in the backyard on a sunny summer day. I do so with DuraTex, it comes out as hard as a rock.
    +1, good hot day, and some direct sunlight is all you need.

    Leave a comment:


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

    'Bake' it in the backyard on a sunny summer day. I do so with DuraTex, it comes out as hard as a rock.

    Leave a comment:

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