what should I use to remove the mold release? Whatever I used didn't work. I tried 409, mineral spirits, and rubbing alcohol. Before I go about spraying again, I want to make sure I get this stuff clean. Does it need to be roughed up with sand paper first? I did that a little, but it didn't take anywhere, even the area's I sanded.
pjpoes said:
The photos look like there is still an abruot change in crvature where the waveguide meets the baffle. By "flush" you mean that you got rid of this sharp edge?
pjpoes said:
I use acetone or MEK. I don't find that the surface need to be roughed as long as its clean. But it does need to be clean and it takes something strong to get the mold release off. It may be that Bins won't stick to poly. I actually haven't tried yet. But the primer that I used stuck fine, no problems.
Matt - speakers are looking great.
I have a large collection of test blocks (approx 2x3" in area, made up from three layers of 3/4" MDF) that I'd glued with various products, and painted with various coatings.
I dug out the tin of Zinnser I had, and sanded down one of the Cascamite glued blocks. I've brushed a couple of coats on, and will finish it in time and see if any lines appear.
Can I ask how you sprayed the BIN? I've got a compressor and a couple of HVLP guns. What pressure and needle size did you use, and did you thin it?
As for using an auto shop for painting - I found what's worked well for large projects is to prime and paint the box, carefully flat it with wet paper, then get my local shop to chuck a couple of coats of 2k clear on it.
Obviously they use clearcoat often, so my guy will sometimes do this for beer money (as it's basically overspray from his point of view).
I have a large collection of test blocks (approx 2x3" in area, made up from three layers of 3/4" MDF) that I'd glued with various products, and painted with various coatings.
I dug out the tin of Zinnser I had, and sanded down one of the Cascamite glued blocks. I've brushed a couple of coats on, and will finish it in time and see if any lines appear.
Can I ask how you sprayed the BIN? I've got a compressor and a couple of HVLP guns. What pressure and needle size did you use, and did you thin it?
As for using an auto shop for painting - I found what's worked well for large projects is to prime and paint the box, carefully flat it with wet paper, then get my local shop to chuck a couple of coats of 2k clear on it.
Obviously they use clearcoat often, so my guy will sometimes do this for beer money (as it's basically overspray from his point of view).
gedlee said:
The main reasons are a combination of space (not much) and UK weather (generally bad).
I have to do my spraying outdoors, and the number of days in the UK where you can guarantee it's going to be both calm and dry (and at a weekend) are pretty few. I can get away with spraying paint and accepting the odd suicidal insect or spec of dust, as I can sand them out, then get a clear coat put on in a spray booth.
I can apply clear coat if I'm planning to wet sand it with fine grits, then polish, but it's far easier if the clear coat goes on perfect - something that's hard for me to do with my equipment and (lack of) workspace.
Oh yeah, and 2k clear coat is obviously rock hard (great) but very dangerous. So if you wanted to avoid spraying nerve gas then it is a way of doing your painting (with something safer), and getting the tough finish put on by the auto shop.
Ok thanks for the advice on what to clean the waveguide with.
As for the transition, yes, I removed the sharp edge. Maybe I didn't make it quite as smooth as transition as you do, but it feels smooth to the touch. There is no sharp lines or edges in the transition that I can feel.
As for how I sprayed the BINS, it says not to thin the product at all, so I didn't. I basically poured it straight into the container. I sprayed with 40 psi of pressure at the tank outlet. and with a cone shaped spray pattern. It wasn't an HVLP gun, it was the inexpensive Campbell Hausfeld general purpose spray gun. I bought it because I wasn't sure about spraying the primer, and was worried it might ruin my good hvlp's. This gun worked surprisingly well, and I would have no problems using it to spray a painted finish as well.
Ok this may seem like a dumb question, but how do you spray the thin mdf edges of the rear panel? I can hand paint them fine, but as for spraying, I get more overspray on the front and back than I do paint on the edges. I've tried changing the pattern, but can't seem to get it right for the edges.
As for the transition, yes, I removed the sharp edge. Maybe I didn't make it quite as smooth as transition as you do, but it feels smooth to the touch. There is no sharp lines or edges in the transition that I can feel.
As for how I sprayed the BINS, it says not to thin the product at all, so I didn't. I basically poured it straight into the container. I sprayed with 40 psi of pressure at the tank outlet. and with a cone shaped spray pattern. It wasn't an HVLP gun, it was the inexpensive Campbell Hausfeld general purpose spray gun. I bought it because I wasn't sure about spraying the primer, and was worried it might ruin my good hvlp's. This gun worked surprisingly well, and I would have no problems using it to spray a painted finish as well.
Ok this may seem like a dumb question, but how do you spray the thin mdf edges of the rear panel? I can hand paint them fine, but as for spraying, I get more overspray on the front and back than I do paint on the edges. I've tried changing the pattern, but can't seem to get it right for the edges.
Acrylic clear coats are both safe and get very hard, albeit it takes days to cure instead of hours. It's the cure time that drives industry to use the more exotic paints, and now the powered paints, which are almost an instant cure. Actually most automotive paints are acrylic, but with an acererator to speed the cure. Its the accelerator that is toxic, not the paint.
I find the water-based acrylic finish to be just as good as the 2k stuff when all is done. And you can't paint 2k over water based acrylic so use of this top coat dictates a more exotic base coat.
I find the water-based acrylic finish to be just as good as the 2k stuff when all is done. And you can't paint 2k over water based acrylic so use of this top coat dictates a more exotic base coat.
pjpoes said:
This has been a pain for me as well!! I am thinking about puting a small radius on those edges to make them easier to paint. But a suggestion is to paint those first and get them the way you want them (remember they are in the back!) then continue on with the front. That way any overspray is on the rear and not on the front.
Paint is a pain, no way around that. There is always going to be a surface that is very tough to do. I usually don't do the bottoms and then put something on the bottom like felt.
I'm finding very small imperfections after spraying the second coat of primer on all of the cut edges. It looks like the small spaces between the raised grain. If I just sand it, it goes to bare wood, expands, and the problem gets worse. I tried the surface glaze, but they are too small for that. Would a thicker coat of primer be best, and then sand that down a little?
gedlee said:
Interesting. I've used cellulose and urethane based paints, but not acrylic.
I wanted to find a single pack product that would seal MDF (John has suggested Varathane), and then I could use a similarly (relatively) low toxicity paint - water based would be desirable.
However, I can't get the Varathane here (which is why I'm interested in the results using BIN), and water based automotive paint is exceptionally expensive in the UK.
BTW (Ant) ShinObiWan sent me a couple of public domain DVDs on spraying techniques, and one showed a company doing auto work, spraying water based paints. They finished the bodywork with a 2k clear coat, so I guess it can't have been a water-based acrylic.
Having said that, I recall that John says he sprays water-based (floor paint I think) and finds it polishes up nicely. So for speakers, no clear coat is required.
gedlee said:
Yep. That matches my experience - paint, sand, paint, sand etc. etc.
With the 2k Urethane paint, I found that spraying MDF edges repeatedly over several hours (it just soaks and soaks the paint) worked well. It basically appears to 'plasticize' the MDF. Once dry, a sand and final painting job usually worked OK. It's just that the first step is very expensive on the paint.
EDIT: Matt, thanks for the info on the spraying. Do you know what the needle size is on the gun you were using?
Varathane is just a brand name for polyurethane. Very stinky stuff, used for floor and I used ti use it as a sealer, but it takes SOOO long to dry. Bins is very fast drying and seals really well.
My prefered paint is acrylic, but its NOT one coat stuff and its slow to cure. It takes daya for a clear coat to dry hard enough to polish. The two part polys can be polished in 24 hours - big difference when time is a factor. You can paint 2k over the automotive acrylics, but, like you say, those are very expensive. Try Rust-O-leum for acrylics.
Basucally, I just make my own acrylic paint from a basically clear binder that I get from Cash coatings. Just mix in a good (heavy pigment) art paint for the color you want and spray that on the Bins base. It usually takes more coats when you mix it yourself because its hard to get enough pigment into the paint. SOmetimes a flow aditive is desirable.
Top this off with the binder with no pigment and polish. Great finish. Inexpensive, just takes a long time.
My prefered paint is acrylic, but its NOT one coat stuff and its slow to cure. It takes daya for a clear coat to dry hard enough to polish. The two part polys can be polished in 24 hours - big difference when time is a factor. You can paint 2k over the automotive acrylics, but, like you say, those are very expensive. Try Rust-O-leum for acrylics.
Basucally, I just make my own acrylic paint from a basically clear binder that I get from Cash coatings. Just mix in a good (heavy pigment) art paint for the color you want and spray that on the Bins base. It usually takes more coats when you mix it yourself because its hard to get enough pigment into the paint. SOmetimes a flow aditive is desirable.
Top this off with the binder with no pigment and polish. Great finish. Inexpensive, just takes a long time.
Well I just wanted to say that I have had very excellent results with the BIN product. For final coats I do recomend spraying it. Even if you don't own a sprayer, at least buy the BIN in spray cans for the final coats. I found that sanding a hand applied coat is fine for the initial coat, but is undesirable for the second/third coats.
I also used some of the Rust-o-leum black primer yesturday. I bought it in a spray can as they had no buckets, and was concerned at the finish quality initially. After leaving it over night, it levels off perfectly and looks quite amazing. I will need to give it a very light wet sanding before applying the black satin, but I think you can get very good results with spray cans. I used a bucket of hot water to keep the cans warm, which I recomend. I also had to keep cleaning the nozzle to keep spatter down.
I'm also finding that the waveguide isn't taking paint like the mdf does. In fact, given it's more perfect surface, I expected it to be smoother, but its far rougher. It might be the conical shape causing paint to lay up less evenly. It is sticking though, it just needs time to set. At least 24 hours before touching it.
Not suprsingly I need to buy more sand paper. You go through paper really fast when doing things right. I should have ordered sand paper via an online dealer, saved a bit of money. In fact, I should have bought everything online and saved money. It was more expensive through the local hardware and auto stores, and added up quick.
I also used some of the Rust-o-leum black primer yesturday. I bought it in a spray can as they had no buckets, and was concerned at the finish quality initially. After leaving it over night, it levels off perfectly and looks quite amazing. I will need to give it a very light wet sanding before applying the black satin, but I think you can get very good results with spray cans. I used a bucket of hot water to keep the cans warm, which I recomend. I also had to keep cleaning the nozzle to keep spatter down.
I'm also finding that the waveguide isn't taking paint like the mdf does. In fact, given it's more perfect surface, I expected it to be smoother, but its far rougher. It might be the conical shape causing paint to lay up less evenly. It is sticking though, it just needs time to set. At least 24 hours before touching it.
Not suprsingly I need to buy more sand paper. You go through paper really fast when doing things right. I should have ordered sand paper via an online dealer, saved a bit of money. In fact, I should have bought everything online and saved money. It was more expensive through the local hardware and auto stores, and added up quick.
Matt
I also recommend spray cans to hand paint.
As to the waveguide, I suspect the fact that you can't get down into it causes more roughness of the surface (its mostly overspray), I find this too. I hope that you are not spraying too much paint down the throat - I don't spray any - since the buildup can get to be significant. And don't mask it as this causes a ridge. Best is to just let the film thickness slowly diminish towards the throat.
At any rate roughness in the waveguide is an advantage as this helps the foam plug to stick and you can't see it once the plug is installed anyways. I never bother to sand the waveguide surface except right at the round-over.
I also recommend spray cans to hand paint.
As to the waveguide, I suspect the fact that you can't get down into it causes more roughness of the surface (its mostly overspray), I find this too. I hope that you are not spraying too much paint down the throat - I don't spray any - since the buildup can get to be significant. And don't mask it as this causes a ridge. Best is to just let the film thickness slowly diminish towards the throat.
At any rate roughness in the waveguide is an advantage as this helps the foam plug to stick and you can't see it once the plug is installed anyways. I never bother to sand the waveguide surface except right at the round-over.
thanks for the pointers, I will keep that in mind.
Anything wrong with using sandpaper to smooth the transition from painted surface to unpainted surface? I did mask initially, but then did the last few coats with no mask, just for the reason you mentioned. I was using 320 grit sandpaper to smooth the transition.
I sanded all three enclosures and rear panels. I decided to respray another good coat of black primer on one of the enclosures and all three rear panels. However I have found too many problems in the other two enclosures that I think another coat of BIN will fix. I'm going to spray those and see how they look. Then spray a coat of black primer on those if all is well. I'm hoping to finish the rear panels today so I can begin the crossovers tomorrow.
Anything wrong with using sandpaper to smooth the transition from painted surface to unpainted surface? I did mask initially, but then did the last few coats with no mask, just for the reason you mentioned. I was using 320 grit sandpaper to smooth the transition.
I sanded all three enclosures and rear panels. I decided to respray another good coat of black primer on one of the enclosures and all three rear panels. However I have found too many problems in the other two enclosures that I think another coat of BIN will fix. I'm going to spray those and see how they look. Then spray a coat of black primer on those if all is well. I'm hoping to finish the rear panels today so I can begin the crossovers tomorrow.
gedlee said:
Yes, but polyurethane what? This is a problem I've had with trying to find an equivalent here in the UK. I can get polyurethane floor varnish, but I've not found a single outlet (even specialist paint suppliers) that could find me something that was technically similar. I did ask the US manufacturer (can't remember who off the top of my head - could be Rust-O-leum) and they couldn't even sell me a single tin on import, as they don't have the paperwork to sell into the EU.
However, as you say, the BIN looks to work well, and I'm going to investigate more - if it's successful then not being able to get the polyurethane is irrelevant!
pjpoes said:
Hoping this isn't a dumb suggestion but I've found that wet sanding is far more effective (and makes the paper last much longer). Soaking the paper in a bucket of water, with a little washing up liquid (dish soap in the US?) works really well.
In fact, you've made me remember why I wasn't using the BIN for speakers - the first speakers I ever made were primed with Zinnser 1-2-3 (a waterbased product) and I did also experiment with BIN. I had loads of problems with the brushed on primer clogging the paper, and the paper overheating and 'tearing' the primer. I didn't have any spraying gear at the time, and didn't know about soaking the paper first. Had I done that, I suspect it'd probably have worked.
gedlee said:
Yeah - this is why I'm looking at casting (from concrete!). I'd probably still paint, but it surely can't be harder to get a good finish than lots of layers of MDF!
I think it will be. The concrete is very porous. I also don't see how concrete is really all that great of a material for a speaker enclosure. Additionally, it's likely to be very heavy and hard to work with.
I think casting in materials like polyurethane resins with additives such as marble powder is a better idea. Do what you want though, and good luck if it works out. MDF is a nice material, its easy to work with, inexpensive, has good acoustic properties. If money was no object I would probably use a cast enclosure made of some exotic materials (I'm sure Dr. Geddes feels the same way), but that simply isn't the case for us. Especially with regard to DIY where we will make one of something. I mean, to make a mold only to make one pair of speakers, wow.
I think wet sanding is fine for finish sanding, but I've never wet sanded for the rougher grits. Maybe that is wrong on my part, but when I use below 220 I use regular paper. I also worry about using wet sanding on mdf during the early sealing process. I feel most comfortable only using wet sanding once the speaker is thoroughly coated in sealer and paint, such that no part of the mdf is exposed or has any chance of being exposed.
I've heard of the trick of adding soap to the water, but this concerns me. Paint won't stick to soap, and while its a very slight amount, isn't there a chance that the soap may leave a residue making future coats of paint problematic? Is the soap quantity too small to matter?
Oh I had the same problem with the BINS that you mention. It only does that if you sand too soon after spraying. At least that was my experience. The BIN takes 24+ hours to really be sandable, especially if its laid on thick. 24 hours is the recommended cure time in 70 degree heat with relative low humidity. This can be accelerated with Curing UV lights (I tried this), but not by much. The biggest imperfections in my speakers right now are because I tried to sand after just 12 hours and the BIN wasn't cured yet. In fact, 24 hours later, left in the 50 degree garage, the BIN wasn't cured either. You have to take your time with that stuff. I moved more portable heaters and picked up another cure light the other day to deal with that, as the paint finish takes 1-2 days minimum to cure. It's now been 12 hours and clearly the paint is not cured yet, with cure lights on for 4 hours, and heats going through the night to get temps to around 70 degrees.
I think casting in materials like polyurethane resins with additives such as marble powder is a better idea. Do what you want though, and good luck if it works out. MDF is a nice material, its easy to work with, inexpensive, has good acoustic properties. If money was no object I would probably use a cast enclosure made of some exotic materials (I'm sure Dr. Geddes feels the same way), but that simply isn't the case for us. Especially with regard to DIY where we will make one of something. I mean, to make a mold only to make one pair of speakers, wow.
I think wet sanding is fine for finish sanding, but I've never wet sanded for the rougher grits. Maybe that is wrong on my part, but when I use below 220 I use regular paper. I also worry about using wet sanding on mdf during the early sealing process. I feel most comfortable only using wet sanding once the speaker is thoroughly coated in sealer and paint, such that no part of the mdf is exposed or has any chance of being exposed.
I've heard of the trick of adding soap to the water, but this concerns me. Paint won't stick to soap, and while its a very slight amount, isn't there a chance that the soap may leave a residue making future coats of paint problematic? Is the soap quantity too small to matter?
Oh I had the same problem with the BINS that you mention. It only does that if you sand too soon after spraying. At least that was my experience. The BIN takes 24+ hours to really be sandable, especially if its laid on thick. 24 hours is the recommended cure time in 70 degree heat with relative low humidity. This can be accelerated with Curing UV lights (I tried this), but not by much. The biggest imperfections in my speakers right now are because I tried to sand after just 12 hours and the BIN wasn't cured yet. In fact, 24 hours later, left in the 50 degree garage, the BIN wasn't cured either. You have to take your time with that stuff. I moved more portable heaters and picked up another cure light the other day to deal with that, as the paint finish takes 1-2 days minimum to cure. It's now been 12 hours and clearly the paint is not cured yet, with cure lights on for 4 hours, and heats going through the night to get temps to around 70 degrees.
sploo said:
Paints are composed of "binders, pigments and volitiles". The volitiles leave the paint when it is "curing" and are fully gone when the paint has cured. There are several paint "binders", but today, basically three, Polyurethane, Acrylic and epoxy. Note that all three are plastics. When you consider the volitile "reducers" for each of these binders then these become a myriad of different products. There are lots of reducers (thinners that keep the binder from solidifying), but the most common are water, and acetone or MEK, a keytone.
Varathane is basically a floor finish. These finishes tend to be "oil" based, which means the reducer is an oil thined with some other volitile. It takes a very long time to dry, the oil does that, which is good on a floor, because it self levels. But this is not a good paint for cabinets. There are also "acelerators" which cause a reaction in the paint and accelerates the cure. Two part polyurethanes have a reducer and an accelerator, which allows them to dry very rapidly, but the binder is still polyurethane just like Varithane floor finish.
The more modern paints are acrylics as these have excellent finish properties, are inexpensive and flow well. Acrylics can be waterborne, volitile or can have accelerators, i.e. 2 part. These later are sometimes called Acrylic-enamel.
So basically you pick your binder, the kind of wait time you can live with and the rest is given.
Epoxy is, of couse, always a two part. This is a great paint, very durable, the best floor finish, but can be quite difficult to work with. It has very low odor which is a real asset in some circumstances. Water based Epoxy does not work well on MDF. No water volitile paint will work very well on MDF because the water swells the material. The faster it cures the less material swelling. This is what makes Bins so good (a unique alchohol volitile which evaporates very fast).
Learn to buy paint by its chemical composition and not its brand name. You'll always get what you want that way.