Good luck with the painting - unless you're well practiced, gloss of any color on MDF is a whole other world of pain.
Looking at your initial sketch again, I'd suggest adding vertical bracing from the top to at least the longer panel that comprises the top of slot port.
Looking at your initial sketch again, I'd suggest adding vertical bracing from the top to at least the longer panel that comprises the top of slot port.
Guess I'll change to matte then. I want colors that are similar to the ones on the Jamo J112 here:
http://www.areadvd.de/images/2015/07/Jamo-J-112-Sub-Front-Seitlich4.jpg
The black doesn't seem to be gloss, but I don't know about the white.
It's too late for changes in the build, though. The carpenter said it'll be ready by Thursday so it's probably mostly ready by now.
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Gloss on any wood is fun, grain filling! anyone...
Then scraping, then filling, then scraping, then the first coat...
I use a wet rot treatment on bare MDF then very light sanding up to 2500 grit.
Then scraping, then filling, then scraping, then the first coat...
I use a wet rot treatment on bare MDF then very light sanding up to 2500 grit.
According to Jamo's website, the finish on the J112 is "High Gloss Polymer Veneer" finish - which could mean prefinished "veneer / laminate" on the raw MDF box. If you definitely want to paint, I'd blast a quick initial seal coat of shellac, but allow several weeks for the fabrication to stabilize before final sanding and painting. There have been numerous threads addressing the subject of just how much fun painting can be.
I'll gladly spend the far lower cost in time and materials to apply either plastic laminate or wood veneer to a box - of course if you're looking for and fancy edge profiles, those options are off the table.
I'll gladly spend the far lower cost in time and materials to apply either plastic laminate or wood veneer to a box - of course if you're looking for and fancy edge profiles, those options are off the table.
The edges on my box are going to be straight, no fancy rounding or anything. I didn't know plastic laminate is a thing for wood work.
What if I give up on high gloss finish and use "normal" (matte) black and white colors? I saw people painting with Duratex on YouTube and they didn't say a word about applying anything before the Duratex itself. I don't have access to Duratex (no one sells them here), but I wonder if they're special in this regard.
Lastly, does lacquer make surfaces glossy?
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Plastic laminate in this case refers to "High Pressure" = brand names such as Formica, Arborite, Wilsonart, Pionite, etc, etc. Multiple layers of paper or sometimes real wood or engineered veneers, infused with melamine or similar resins and baked under heat and pressure to achieve a thermoset thin sheet. The visible layer is essentially a high quality color print / photograph, which in combination with textured stamping plates can create some very interesting patterns. Usually adhered to wood sheet goods cabinet carcass or countertops with contact cement or white PVC glue.
Unless the cabinet was assembled with mitre folded / glue joint edges, there will be exposed butt joints and the raw edges of MDF to contend with. Those joints are notorious for telegraphing through almost any thin film finish without a lot of prep work - generally several times the fabrication and assembly time for the boxes themselves.
Lacquer is available from flat (less than 10% sheen) to super glossy (90%). When we do any in house "painting" of MDF fabrications (kitchen doors, matching paneling, etc), we'll use several layers of high solid catalyzed primers, followed with perhaps several color coats - also catalyzed. I've air-quoted the word painting above, as the top coat product is actually a catalyzed conversion varnish. No surface finish is bullet-proof, but the M L Campbell Resistant, or Krystal lacquer are pretty tough stuff.
Unless the cabinet was assembled with mitre folded / glue joint edges, there will be exposed butt joints and the raw edges of MDF to contend with. Those joints are notorious for telegraphing through almost any thin film finish without a lot of prep work - generally several times the fabrication and assembly time for the boxes themselves.
Lacquer is available from flat (less than 10% sheen) to super glossy (90%). When we do any in house "painting" of MDF fabrications (kitchen doors, matching paneling, etc), we'll use several layers of high solid catalyzed primers, followed with perhaps several color coats - also catalyzed. I've air-quoted the word painting above, as the top coat product is actually a catalyzed conversion varnish. No surface finish is bullet-proof, but the M L Campbell Resistant, or Krystal lacquer are pretty tough stuff.
Damn, I thought it only takes a single can of glossy paint to get the job done.
So this paint I bought is useless without primer and other materials applied beforehand?
So this paint I bought is useless without primer and other materials applied beforehand?
There are "issues" when applying a finish to MDF. First, the surface isn't very smooth, and second the surface absorbs the finish.
Primers are designed to fill the pores of the surface and be easily sanded. It may take several iterations of applying primer and "block sanding" to get to a truly smooth substrate for final finishing.
Once the surface is prepared properly, you can begin to apply the final finish coats. There are several options available, and you need to know which one you're going to use before you start priming, because some finish products will attack some primers.. .
Fine glossy finishes can take weeks to achieve. Matte finishes are much more forgiving, but the basics are really similar. If you really don't care about how the finish looks, truck bed liner material will likely cover in one coat, but that is not exactly furniture-grade.
Primers are designed to fill the pores of the surface and be easily sanded. It may take several iterations of applying primer and "block sanding" to get to a truly smooth substrate for final finishing.
Once the surface is prepared properly, you can begin to apply the final finish coats. There are several options available, and you need to know which one you're going to use before you start priming, because some finish products will attack some primers.. .
Fine glossy finishes can take weeks to achieve. Matte finishes are much more forgiving, but the basics are really similar. If you really don't care about how the finish looks, truck bed liner material will likely cover in one coat, but that is not exactly furniture-grade.
and with the truck bed liner products I've seen, there's at least as long an off-gassing period as with any high VOC solvent based products such as those by ML Campbell that I named above.
Even if I didn't prefer the look of "real" wood / veneers, I'd still use them as a finish to paint -except perhaps for back panels if I run out of material, or for bottoms of floorstanders.
Even if I didn't prefer the look of "real" wood / veneers, I'd still use them as a finish to paint -except perhaps for back panels if I run out of material, or for bottoms of floorstanders.
I got away with none to start with.
I used a piece of wood on top of the parts being glued to apply pressure.
However I left two pieces drying and came back and the wood had moved and was glued solid 1/4 inch out from where it should be !
So learned my lesson and bought a long clamp and a couple of short ones.
I used a piece of wood on top of the parts being glued to apply pressure.
However I left two pieces drying and came back and the wood had moved and was glued solid 1/4 inch out from where it should be !
So learned my lesson and bought a long clamp and a couple of short ones.
If you are acquiring tools then two or three to start. If you want the project to go quickly, you also need an air nailer. They have kits with guns, tank and hose combined all for a reasonable price. The clamps are used to snug to panels after applying glue. Once you nail, you remove the clamps and move onto the next panel. This works really well when you are using battens or cleats as your fasteners are all blind.
Brute😀
I prefer dowels and weigh got a nail gun that does panel pins bigger would scare me... but good for the instant fit ups, used with mouldings never panels.
I prefer dowels and weigh got a nail gun that does panel pins bigger would scare me... but good for the instant fit ups, used with mouldings never panels.
some tight corners and inside a box with smaller driver opening than, say a 12" woofer can be hard to access for tightening up those pocket screws
Thanks for the details.
How long would it take to apply a decent finish with matte colors?
If I could find glossy white plastic laminate where I live, I'd probably just but it instead but I'm not sure I'll find it.
Do I first buy the paint I want, and then use whatever method is described on the can? For example, the two glossy paints I bought have different instructions. One of them does mention using a primer, and the other flaxseed oil (is that the one you add to food???).
Not sure the quality of mdf you guys are getting, but the stuff i get is not suitable for pocket screws, dowels or even nails for that matter. The core just splits open along the edges, i find biscuits to be the strongest and least damaging.
I find mdf good for making shop jigs and fixtures.... not much else
I find mdf good for making shop jigs and fixtures.... not much else
I picked up the assembled enclosure this morning. Luckily I brought the woofer to the carpenter's workshop, because the outer front baffle's circular cut needed some fixing.
I noticed that the glue the carpenter used didn't expand between the sheets of MDF, so I'm afraid it may not be completely sealed (at least as far as sealing with glue is concerned). Can I use silicone in the interior edges of the box in case the current sealing isn't enough? And how can I check if it's actually sealed or not?
I was at the local hardware store just now and was told that if I'll apply wood filler all over the enclosure, I should be able to then apply whatever paint I want over it, matte or glossy. What do you think?
I noticed that the glue the carpenter used didn't expand between the sheets of MDF, so I'm afraid it may not be completely sealed (at least as far as sealing with glue is concerned). Can I use silicone in the interior edges of the box in case the current sealing isn't enough? And how can I check if it's actually sealed or not?
I was at the local hardware store just now and was told that if I'll apply wood filler all over the enclosure, I should be able to then apply whatever paint I want over it, matte or glossy. What do you think?
Where I work we go through several thousand sheets of MDF, cabinet grade melamine and shop grade plywood for cases and lay-up cores per year. The premium grade MDFs we get from States, Plum Creek, West Fraser, Ranger, Medite Corp don't generally suffer from those problems, but precautions are still required such as no fasteners within at least 2" of corner of edge, proper pilot drilling, and use of only lo-root type of screws.
Don't even think about the Ultra-lite varieties of MDF for anything other than cabinet doors.
When dealing with architect's specs and/or subject to inspection by AWMAC* you sometimes have no choice on commercial projects.
* on certain construction grades of AWMAC inspected jobs, we're required to use 2" screws at 4" centers on the back panels of floor standing cabinets - on a tall wardrobe that can mean over 60 screws on a 1/2" thick back panel, which will then be anchored to the wall with maybe a total of 6?
sorry, just one of my pet peeves
notwithstanding the above - I couldn't agree more
Well, a clean glue joint edge cut on a decent table saw shouldn't need to rely on "expansion" of glue if properly clamped and screwed / brad nailed together .
If you can access all the internal joint edges, then a thick bead of silicone caulking should help. As the box design in original drawing was vented and also showed a large opening on rear panel that I'd assume is for plate amp, to test for air tight seal on the panel joints would actually be a bit tricky.
I think the advice to apply wood filler over the entire enclosure is more for the benefit of the folks selling you the filler. All that needs filling would be any screw holes, and exposed edge grain of the MDF - still not as easy as it sounds.
There will also of course be sanding required, which I would suggest to all surfaces to be painted, before your prime coats. Most MDF panels have a heat tempered/ polished surface to the faces, which without proper sanding and priming will very likely telegraph the locations of any filled screw holes and raw edges through almost any thin film finish .
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