gedlee said:
I couldn't agree more. In the end it doesn't matter how hard it was to paint your cabinets but what the surface looks like.
Best, Markus
I use soap in the water too. Its a small amount, but I do always clean the surface before spraying again. NEVER wet sand MDF unitl it is fully sealed. Even a small pin hole will be a problem. And if you accidentally sand through the seal when wet, you can basically start over.
pjpoes said:
My hope is more one of consistency (both in terms of density/porosity, and stability under temperature changes). There's also the possibility of adding aggregate and polishing, to get an attractive end result without any painting (though I must admit I have no knowledge of the practicalities of this).
Polyurethane resins with additives are something I should certainly look at. I'm not sure how the cost compares to concrete, but I suspect it would be more expensive.
My (crazy) plan is to try to make small runs of speakers, so the time taken to work out a good molding system would be worth the effort (I hope).
pjpoes said:
Ah yes, I wouldn't wet sand on anything more coarse than 400 grit. As you say, you don't want to risk wetting the MDF, so I only tend to do it wet when the surface is already pretty smooth and there's plenty of primer on. Of course, the rougher grits tend to clog up a little less, so there's less need for wet sanding. Better quality paper really does seem to make a difference too.
As for the soap - I usually add just a small squirt into a bucket (no foam/bubbles), and anything I've wet sanded will be well washed down with clean water afterwards.
Casting my mind back a long way, I suspect it was the 1-2-3 product that I really had problems with. I recall priming the speakers, then pretty much destroying the coating with sanding (it made a real mess - coming off like rubber). I completely stripped it all off, primed again, and left the speakers in my airing cupboard (>75F) for a week. Sanding it made the same mess again, so I used a roller to give a stippled affect, then sprayed paint cans on top, and accepted that. Never occurred to me to wet sand!
gedlee said:
Many thanks for the detailed info Earl.
I was using the Varathane MSDS to try to find something of a similar composition, but struggled to find an equivalent here. As you say, water and MDF are a very bad combination, so I do avoid anything like that.
Believe me, I've tried many many different products over the years on MDF, from epoxies, to damp proof sealers, to oil based, single pack, two pack (hardener). I've probably sniffed more chemicals in the process than your average drugged up teenager 😉.
I have a model aircraft building friend who's using epoxy paints, and he coated a block for me as a test a while back. I've never got round to flatting and polishing it to see how it will behave. Partly this is because it's a very expensive product, so it's one that wouldn't be such as practical route for me.
I've found that with paint the cost truely reflects the quality. I have not had much success with "bargin" paints (except the ones I make myself).
If you want good finishs at the lowest cost then make the paint yourself. I am a model builder and they will tell you that all paint is not the same. But I got tired of the ridiculous prices so I started mixing my own. Then I got to getting raw acrylic binder - basically a good water-based acrylic cabinet finish, and mising the colors myself. The paint that I make that way works great. There is a company called BYK Chemicals in Germany that sells and tells you everything that you need to know about paint, although they don't make paint. They only make additives. But it is the aditives that make the paint great.
If you want good finishs at the lowest cost then make the paint yourself. I am a model builder and they will tell you that all paint is not the same. But I got tired of the ridiculous prices so I started mixing my own. Then I got to getting raw acrylic binder - basically a good water-based acrylic cabinet finish, and mising the colors myself. The paint that I make that way works great. There is a company called BYK Chemicals in Germany that sells and tells you everything that you need to know about paint, although they don't make paint. They only make additives. But it is the aditives that make the paint great.
sploo said:
Are you set on doing your own designs? I'd entertain someone making my speakers in EU because shipping costs kill the benefit. But if they were made their it would be quite cost effective.
Hey Dr. Geddes, Any recommendation on a Satin black paint? Again, Satin, not Flat. My understanding is that Satin is a mix of gloss and flat at a specific ratio such as 60/40, where as semigloss is more like 80/20. I bought Rustoleum satin black, but I'm not loving the finished product. It's not from the professional coating line and isn't what I thought it was.
I suppose I could buy a can of flat and a can of gloss and mix my own in the desired ratio. Would this be your recommendation? The stuff I got is from the line with rust inhibitors (I didn't see that when I bought it), and I believe includes some of the same materials as the metal primers they sell. The biggest problems is that it seems to build up in strange ways that the primers I used did not. It doesn't flow all that well and thus isn't leveling great. Also, it's taking forever to dry. One of the rear panels was sprayed well over 24 hours ago and still feels a little tacky. This panel has been inside drying at 70 degrees with very low humidity, and was under a UV lamp for a period of time as well. I'm thinking of sanding this down when it dries to a smooth finish and respraying a final coat or two of a more appropriate satin black paint.
Satin Black This is what I am using now and I believe may not be what I want.
Industrial finish satin black this is the only industrial paint I found available in satin, and only in pints, not gallons. It's oil based though, I thought you had suggested a water based version, which I can't find.
I suppose I could buy a can of flat and a can of gloss and mix my own in the desired ratio. Would this be your recommendation? The stuff I got is from the line with rust inhibitors (I didn't see that when I bought it), and I believe includes some of the same materials as the metal primers they sell. The biggest problems is that it seems to build up in strange ways that the primers I used did not. It doesn't flow all that well and thus isn't leveling great. Also, it's taking forever to dry. One of the rear panels was sprayed well over 24 hours ago and still feels a little tacky. This panel has been inside drying at 70 degrees with very low humidity, and was under a UV lamp for a period of time as well. I'm thinking of sanding this down when it dries to a smooth finish and respraying a final coat or two of a more appropriate satin black paint.
Satin Black This is what I am using now and I believe may not be what I want.
Industrial finish satin black this is the only industrial paint I found available in satin, and only in pints, not gallons. It's oil based though, I thought you had suggested a water based version, which I can't find.
This is what I would recommend
http://www.rustoleumibg.com/product.asp?lvl=P&pnv=2&snv=1&pid=10 or
http://www.rustoleumibg.com/product.asp?lvl=P&pnv=2&snv=2&pid=129
But they only have semi-gloss and flat. Satin is a word usually reserved for wall paint and means flat. I'd try the flat and then if it too dull overspray with a little semi-gloss. I believe this paint is sold at Graingers. You can mail order it if there is not one close to you.
http://www.rustoleumibg.com/product.asp?lvl=P&pnv=2&snv=1&pid=10 or
http://www.rustoleumibg.com/product.asp?lvl=P&pnv=2&snv=2&pid=129
But they only have semi-gloss and flat. Satin is a word usually reserved for wall paint and means flat. I'd try the flat and then if it too dull overspray with a little semi-gloss. I believe this paint is sold at Graingers. You can mail order it if there is not one close to you.
water based enamel Would this work? It's flat black, which I think will be a different finish from the Satin I'm looking for, but it's a start, no?
I was able to get a can of water based Acrylic Enamel at the hardware store from another company, but they tinted it wrong. It was very cheap, on clearance for like 6 dollars. I will see if I can't get my money back or another can of this stuff tinted properly. Is any water based acrylic enamel probably acceptable?
I was able to get a can of water based Acrylic Enamel at the hardware store from another company, but they tinted it wrong. It was very cheap, on clearance for like 6 dollars. I will see if I can't get my money back or another can of this stuff tinted properly. Is any water based acrylic enamel probably acceptable?
Why use something else if it doesn't give you the finish you want?
As long as the paint is compatible with the primer you used then there's nothing to worry about. A speaker enclosure is one of the least stressed surfaces in a livingroom.
It's more important how you fill, sand and seal the cabinets. Get them perfectly sealed. Let everything dry until the sealer has completely cured and the MDF doesn't move anymore. The bad news is that this can take weeks if the MDF is not very dense and your sealer uses a very slow drying solvent (e.g. water). Work in an environment that is at normal room temperature all the time.
Best solution is to use only bevel cuts – not an option with rounded corners and edges like the ones needed for Earls' speakers.
Here's what happened to the edges of my Nathans:
The MDF shrinks while drying but it shrinks in one direction only. It basically gets thinner. The difference is smaller than 1/10mm.
Best, Markus
As long as the paint is compatible with the primer you used then there's nothing to worry about. A speaker enclosure is one of the least stressed surfaces in a livingroom.
It's more important how you fill, sand and seal the cabinets. Get them perfectly sealed. Let everything dry until the sealer has completely cured and the MDF doesn't move anymore. The bad news is that this can take weeks if the MDF is not very dense and your sealer uses a very slow drying solvent (e.g. water). Work in an environment that is at normal room temperature all the time.
Best solution is to use only bevel cuts – not an option with rounded corners and edges like the ones needed for Earls' speakers.
Here's what happened to the edges of my Nathans:
An externally hosted image should be here but it was not working when we last tested it.
The MDF shrinks while drying but it shrinks in one direction only. It basically gets thinner. The difference is smaller than 1/10mm.
Best, Markus
pjpoes said:
I use that exact paint (even that color). It works very well. Its also very flat. If you want a more satin sheen then overcoat it with a satin clear acrylic. All "satin" and "flat" finishes just have a little talc mixed into the paint. You can get a really nice surface by adding glass beads. Once dry, you can scrub the finish with a stiff brush - which I suggest to dislodge and nearly loose beads - and it won't affect the suface at all. Its very durable and looks great. I've sold many speakers with that paint on them.
well after 4 different attempts at making black, they finally managed to make a very dark charcoal color (it's still not black). It's water based acrylic enamel, and I sprayed some test pieces to see how I like it. It has almost no odor, dries to the touch in 25 minutes, and can be resprayed in an hour. I like this much better than the other stuff. Though I will say the other stuff did leave a nice finish once dry. I don't want brain damage trying to finish these speakers, so lets see how this stuff works out.
I find that picture in post #150 interesting. If mdf shrinks 0.1mm in thickness wouldn't that suggest that it would be better to dry it thoroughly before assembly? I would think that much shrinkage would put a little unnecessary stress on the glued surface for the life of the box, where if it were allowed to dry first this could be avoided.
By the way, years ago when I was building lots of boxes out of plywood and particle board (not mdf) I did a little experiment where I made a series of glued butt joints using white (water based casein) glue to test a notion I had regarding the process by which the glue penetrates the surface. This was brought on by noticing that on a couple of occasions where a butt or miter joint had failed, the surface of the hardened glue indicated very little penetration indeed into the wood surface. My thought was that there was not enough moisture in the glue to properly moisten the wood, but if any more were added, the glue would be too liquid to work with, so the solution might be to add moisture to the wood surface just before applying the glue.
So, in one of the test joints, I wiped the surface with a wet (not damp) sponge just before gluing. I added a trace of detergent to the water on the sponge. The idea was to break down the surface tension to draw the glue into the wood fibers. Those particular joints were much stronger than any others and the failure was never at the junction per se, but within the wood fibers themselves. With plywood for example, the laminations would be pulled apart and the break would be near, but not at the interface.
It worked so well I have always done this ever since when using white glue on wood of any kind, such as legs and rungs of wooden chairs.
By the way, years ago when I was building lots of boxes out of plywood and particle board (not mdf) I did a little experiment where I made a series of glued butt joints using white (water based casein) glue to test a notion I had regarding the process by which the glue penetrates the surface. This was brought on by noticing that on a couple of occasions where a butt or miter joint had failed, the surface of the hardened glue indicated very little penetration indeed into the wood surface. My thought was that there was not enough moisture in the glue to properly moisten the wood, but if any more were added, the glue would be too liquid to work with, so the solution might be to add moisture to the wood surface just before applying the glue.
So, in one of the test joints, I wiped the surface with a wet (not damp) sponge just before gluing. I added a trace of detergent to the water on the sponge. The idea was to break down the surface tension to draw the glue into the wood fibers. Those particular joints were much stronger than any others and the failure was never at the junction per se, but within the wood fibers themselves. With plywood for example, the laminations would be pulled apart and the break would be near, but not at the interface.
It worked so well I have always done this ever since when using white glue on wood of any kind, such as legs and rungs of wooden chairs.
Russell, I don't think that the MDF needs to dry before glueing. It expands because of the solvents found in glue, filler, sealer and paint. The only way to avoid that is to use products with a fast volatilizing solvent or to wait for a very long time between each step.
Best, Markus
Best, Markus
It would be interesting to use one of those moisture meters meant for lumber (the kind where you drive a small spike into the end or edge grain and it reads out moisture in percent) and measure the percentage when you buy it and after a few days indoors in a 50% rel humidity environment. I suspect it is typically stored in high relative humidity conditions in the lumber yard and household humidity averages 30 - 70%, I think.
Anyway - I guess it would lose the excess fairly quickly (1-2 weeks?). The second part of the experiment would be to measure the thickness at a few different spots with a micrometer when bought and after a couple of weeks.
Just musing. That's the kind of thing I would have going on in the background while I am building - which I haven't done for ages. I might get a scrap of mdf from the local yard and do the micrometer thing anyway.
Anyway - I guess it would lose the excess fairly quickly (1-2 weeks?). The second part of the experiment would be to measure the thickness at a few different spots with a micrometer when bought and after a couple of weeks.
Just musing. That's the kind of thing I would have going on in the background while I am building - which I haven't done for ages. I might get a scrap of mdf from the local yard and do the micrometer thing anyway.
Ok well they aren't finished yet, but here is a shot of one of the speakers drying. The paint needs to set overnight before I'll make any final decisions on the finish. This is the satin charcoal water based urethane acrylic paint. I had to add a leveling agent and some water to get it to flow right, but it looks pretty good to me. Also, I think I like the charcoal look better than straight black.
In this last one you can see a slight run. It's actually under the paint, in the BIN layer I sprayed. I sanded it smooth, but it keeps showing up. It's so hard to see I may just leave it for now.
Did I mention how much I like water based paint? The other paint had me seeing things.
In this last one you can see a slight run. It's actually under the paint, in the BIN layer I sprayed. I sanded it smooth, but it keeps showing up. It's so hard to see I may just leave it for now.
Did I mention how much I like water based paint? The other paint had me seeing things.
Russell Dawkins said:
All the discussion that I've read recommends this and I recommend it in the assembly manual for the kits. I think that its pretty common knowledge. Although the soap is new, I've never heard of that, and I would be suspicious of doing that part of your recommendation as soap does not usually aid adherance. Certainly not of paint.
pjpoes said:
I think that I've said this all along. If you have the time , water based acrylic is superb. If you live in the US, check out Cash Coatings for a very fine acrylic paint that does everything right.
well I think it looked better than it was. Maybe its the weather, but the finish came off on one of the rear panels when I went to sand it. It came off like a latex, very rubbery. I don't understand, as it's chemical makeup seems very similar to the other product I looked at from Rust-o-leum. I have purchased the other product, but because of the weather, I have decided to repaint that piece with what I have, and refinish these when its warmer. No point in continuing to waste time and money on paint.