aviserated Posted January 26, 2005 Share Posted January 26, 2005 What is the quickist and easiest to use product for sealing MDF before painting with black high gloss lacquer. So far I have used four 11 oz. spray cans of lacquer without using any sealer. Painting and sanding between each coat and the surface still is not smooth enough for polishing to a high gloss without showing imperfections. By the way, these 15 liter bass reflex enclosures are for my Fostex FE167E fullrange drivers that I built using Fostex's recommended enclosure instructions availible at www.madisound.com. These speakers are well worth the the trouble to build and finish. Quote Link to comment Share on other sites More sharing options...
analogman Posted January 26, 2005 Share Posted January 26, 2005 ---------------- On 1/26/2005 4:36:51 PM aviserated wrote: What is the quickist and easiest to use product for sealing MDF before painting with black high gloss lacquer. So far I have used four 11 oz. spray cans of lacquer without using any sealer. Painting and sanding between each coat and the surface still is not smooth enough for polishing to a high gloss without showing imperfections. By the way, these 15 liter bass reflex enclosures are for my Fostex FE167E fullrange drivers that I built using Fostex's recommended enclosure instructions availible at www.madisound.com. These speakers are well worth the the trouble to build and finish. ---------------- Hello, Use a water based polyurethane. Ace brand is good for your purpose. Use the finish coat material, NOT the water based sealer. It will dry hard, sandable and fast. The water based "polys" do produce tiny little bubbles if you use a roller, but can be sanded out easily. When you say "quickest" that means different things to different people. Depending on what you mean by "quick" and if you are willing to wait a few days before final sanding and finish coat, you could use an oil based urethane. It really offers no advantage for your purpose and will cost more. The only upside to oil based in this case is that you may be able to obtain the degree of smoothness you desire with less coats. The water based dries much faster and you can do more coats in far less time. It is also great because you can clean up with soap and water and you've already got a base coat on your project so the water base part won't be an issue. Have fun, Analogman Quote Link to comment Share on other sites More sharing options...
aviserated Posted January 26, 2005 Author Share Posted January 26, 2005 Thanks. Also what grit sandpaper would you recommend for dry sanding in between coats. Quote Link to comment Share on other sites More sharing options...
popbumper Posted January 26, 2005 Share Posted January 26, 2005 Spray the first coat of poly, let dry for 24 hours. Do NOT sand this coat as film thickness is too thin. Spray a second coat; let dry for 48 hours. NOW, sand using 600 grit between this and any subsequent coats to achieve a smooth uniform surface. Once finished sealing with poly, apply final coat; be SURE last poly coat is lightly sanded so the final finish has something to "bite". Be sure to clean the final poly coat with a tack cloth and Naphtha (to remove any fingerprints/unwanted oils/sanding dust) before applying the final coat. Popbumper Quote Link to comment Share on other sites More sharing options...
analogman Posted January 26, 2005 Share Posted January 26, 2005 Hello again, I've tried them all and the best I've used is sometimes hard to find. Ace has had it most of the times I've needed it. "Gold Flex" "Ali-Gator-Grit" is what's printed on the back of the sheets. The cutting side is a light orange in colour. Use the 220 grit. It is wonderful paper, doesn't clog and is the most flexible I have ever used. Seems to cut better the more you use it. If you can't find it, any quality 220 will work, but I promise you this paper is worth the effort. Won't leave the hard lines you get sometimes even when you hand sand. It is expensive, about a dollar a sheet. Buy a whole pack if you like it to have for the next project, if you find it hard to locate. No, I don't work for them, it's just that good! Have fun, Analogman Quote Link to comment Share on other sites More sharing options...
aviserated Posted January 26, 2005 Author Share Posted January 26, 2005 Has anyone ever used automotive sandable primer. I can buy a quart of black primer and a gallon of fast dry lacquer thinner pretty reasonable. It also dries very quickly . I can use my orbital sander, air compressor, and paint gun to speed things up. Quote Link to comment Share on other sites More sharing options...
analogman Posted January 26, 2005 Share Posted January 26, 2005 ---------------- On 1/26/2005 5:36:05 PM popbumper wrote: Spray the first coat of poly, let dry for 24 hours. Do NOT sand this coat as film thickness is too thin. Spray a second coat; let dry for 48 hours. NOW, sand using 600 grit between this and any subsequent coats to achieve a smooth uniform surface. Once finished sealing with poly, apply final coat; be SURE last poly coat is lightly sanded so the final finish has something to "bite". Be sure to clean the final poly coat with a tack cloth and Naphtha (to remove any fingerprints/unwanted oils/sanding dust) before applying the final coat. Popbumper ---------------- I agree with the above except you don't need to go as fine as 600 for the in between sandings until you're down to your last couple of coats of poly. If you use something as fine as 600 for every sanding chances are you'll wind up with visible bumps and pimples when you shoot the black. You'll also need A LOT of paper if you go straight 600 grit and take much longer to get the results you want. If you are shooting a true high gloss lacquer you really don't need to use 600 at all until your final sanding, as it smoothes more than it cuts. Regards, Analogman Quote Link to comment Share on other sites More sharing options...
analogman Posted January 26, 2005 Share Posted January 26, 2005 ---------------- On 1/26/2005 7:18:30 PM aviserated wrote: Has anyone ever used automotive sandable primer. I can buy a quart of black primer and a gallon of fast dry lacquer thinner pretty reasonable. It also dries very quickly . I can use my orbital sander, air compressor, and paint gun to speed things up. ---------------- The auto primer won't flow on the MDF like it will on metal. Not to be short but I've told you what I'd do/have done. Good luck, Analogman Quote Link to comment Share on other sites More sharing options...
popbumper Posted January 26, 2005 Share Posted January 26, 2005 The rationale for using 600 grit is based on the fact that the finished/dry coats are very thin, and you want to take off the least material possible. I have used this product on a number of pinball playfields (which are nothing more than silkscreened plywood), and have never witnessed this "pimpling" you are referring to (on ten different playfields, with a maximum thickness of 9 coats of Varathane). Alternatively, he may want to build a few initial coats first before sanding, though I would NOT suggest anything less than a 400 grit wet and dry at MINIMUM (for the initial sand, followed by finer grits before topcoat). 220 is far too rough, and will create small scratches that will not reveal themseves until the nice glossy topcoat reveals them. I've seen it happen too many times, and going "backwards" is a real pain. Popbumper Quote Link to comment Share on other sites More sharing options...
michael hurd Posted January 26, 2005 Share Posted January 26, 2005 Automotive primer won't flow? Geez, either you don't know how to reduce the material, have the wrong spray gun, or incorrect pressures. I refinish automobiles, and primered quite a bit of mdf with a two-component urethane primer surfacer. You can lay it down just as nice on mdf, so smooth that you just have to knock it down with 600 grit before finishing with a urethane topcoat. Quote Link to comment Share on other sites More sharing options...
analogman Posted January 26, 2005 Share Posted January 26, 2005 ---------------- On 1/26/2005 9:23:16 PM popbumper wrote: The rationale for using 600 grit is based on the fact that the finished/dry coats are very thin, and you want to take off the least material possible. I have used this product on a number of pinball playfields (which are nothing more than silkscreened plywood), and have never witnessed this "pimpling" you are referring to (on ten different playfields, with a maximum thickness of 9 coats of Varathane). Alternatively, he may want to build a few initial coats first before sanding, though I would NOT suggest anything less than a 400 grit wet and dry at MINIMUM (for the initial sand, followed by finer grits before topcoat). 220 is far too rough, and will create small scratches that will not reveal themseves until the nice glossy topcoat reveals them. I've seen it happen too many times, and going "backwards" is a real pain. Popbumper ---------------- You obviously have experience and I'm not debating you. WATER based polyurethanes WILL produce tiny bubbles when applied, to what degree depends on how you do it. You also assume that he has a spray gun, he said in his first post that he was using spray cans. He also asked for the "quickest and easiest". Oil based Varathane and topcoat prep with 400&600 is neither "quick" nor "easy". I also agreed that the final couple of sandings could/should be done with the 600 as you suggested. Regards, Analogman Quote Link to comment Share on other sites More sharing options...
michael hurd Posted January 26, 2005 Share Posted January 26, 2005 Instead of time consuming lacquer, get a pint of automtive alkyd black, and reducer. Three coats of alkyd will dry overnight, and give you a lot of material to sand smooth and polish. If you are looking for a very smooth finish, sand with p1500 hookits on an orbital sander, then polish with a quality foam pad and 3m perfect-it III extra cut rubbing compound. Quote Link to comment Share on other sites More sharing options...
analogman Posted January 26, 2005 Share Posted January 26, 2005 ---------------- On 1/26/2005 9:35:26 PM michael hurd wrote: Automotive primer won't flow? Geez, either you don't know how to reduce the material, have the wrong spray gun, or incorrect pressures. I refinish automobiles, and primered quite a bit of mdf with a two-component urethane primer surfacer. You can lay it down just as nice on mdf, so smooth that you just have to knock it down with 600 grit before finishing with a urethane topcoat. ---------------- Why don't you read my posts with some attempt on your part for accuracy and comprehension. I was addressing the specifics of his question, not attempting to write a treatise on all the possible finishing methods available to Mankind. I'm sure automotive finishes are not supplied with specific reduction ratios for use on MDF,so what you are alluding to is purely anecdotal at best. Are you willing to call this guy up and walk him through what you've learned by trial and error and experience? I gave him PRACTICAL advice. The question was not "who knows the most about finishes" or "whose finishing methods are best". I've been in the auto industry for nearly thirty years and can say with certainty that 95% of all "body men" are hacks. With regards, Analogman Quote Link to comment Share on other sites More sharing options...
michael hurd Posted January 26, 2005 Share Posted January 26, 2005 You certainly can't paint everyone with one brush! Regardless if 95% of who you know are hacks, there are some people that take pride in their work and repair vehicles correctly. He mentioned that he had a spray gun and possibly getting some lacquer primer. You certainly could use lacquer, but a urethane product makes a much better base, builds much faster and sands just as nice. Sure, if he wants advice, pm me and I will walk him through it. I really don't care if he does or doesn't. Quote Link to comment Share on other sites More sharing options...
popbumper Posted January 26, 2005 Share Posted January 26, 2005 Analogman: ...nor did I wish it to be a debate, I just wanted this guy to hear all sides/details for his benefit. Some additional notes: 1) ALL the application I have done is using water based material in spray cans. I have never had an issue with bubbles, but HAVE had with dust (it's almost impossible to avoid). This was also in a non-humidity controlled environment, though I did make sure the air was not moving (no fans on), and I was wearing a respirator mask. 2) I never assumed he had a spray gun. When using cans (which is easiest), spray a nice WET, thick coat so that when the light hits it, the whole surface looks like water (wet/deep). It will shrink back into the surface and film as the water evaporates. 3) Water based Varathane application/prep IS easy, IMHO. You just can't hurry it - it takes a few days to apply enough coats, and then it needs to cure for at least two weeks before you coat it. You can teel it is dry when the faint odor of ammonia disappears entirely. Not having heard from the original poster for a while, I hope between all of us he is taking notes/learning something!! Popbumper Quote Link to comment Share on other sites More sharing options...
analogman Posted January 27, 2005 Share Posted January 27, 2005 ---------------- On 1/26/2005 11:48:13 PM popbumper wrote: Analogman: ...nor did I wish it to be a debate, I just wanted this guy to hear all sides/details for his benefit. Some additional notes: 1) ALL the application I have done is using water based material in spray cans. I have never had an issue with bubbles, but HAVE had with dust (it's almost impossible to avoid). This was also in a non-humidity controlled environment, though I did make sure the air was not moving (no fans on), and I was wearing a respirator mask. 2) I never assumed he had a spray gun. When using cans (which is easiest), spray a nice WET, thick coat so that when the light hits it, the whole surface looks like water (wet/deep). It will shrink back into the surface and film as the water evaporates. 3) Water based Varathane application/prep IS easy, IMHO. You just can't hurry it - it takes a few days to apply enough coats, and then it needs to cure for at least two weeks before you coat it. You can teel it is dry when the faint odor of ammonia disappears entirely. Not having heard from the original poster for a while, I hope between all of us he is taking notes/learning something!! Popbumper ---------------- I'm sorry, I thought it was obvious that I wasn't talking spray cans when I mentioned rollers. Why waste money on spray cans when you're going to sand between coats? Regards, Analogman Quote Link to comment Share on other sites More sharing options...
michael hurd Posted January 27, 2005 Share Posted January 27, 2005 It was the original poster aviserated that mentioned using spray cans. Water based poly is not a good suggestion at all on a product that sucks up water like a sponge. Regardless, you need to be able to seal the surface before trying to paint it, otherwise you can pour thin paint on until the cows come home, without ever getting a glossy finish. To seal the mdf, use a quality primer, be it of the alkyd variety ( home variety ) applied liberally with a roller, or a 2 component automotive urethane primer surfacer applied with a spray gun. Then you can go ahead and apply the topcoat of choice. Quote Link to comment Share on other sites More sharing options...
popbumper Posted January 27, 2005 Share Posted January 27, 2005 Analogman man asked: "Why waste money on spray cans when you're going to sand between coats?" 1) Spray cans are user friendly. They take up little room, need no special equipment/mixing, are inexpensive, less material is wasted, and anyone with a forefinger can use them. 2) Sanding, especially with fine grits, does not remove an appreciable amount of material (as you noted - they SMOOTH rather than CUT), so you are not going to "waste" much anyway. Not sure why you would ask that? Popbumper Michael: This may not be the best "filler", agreed, BUT, once the initial films adhere to the surface and dry, the base material will quit "soaking up" the spray. Primer would probably be the best option. I guess the greater lesson here is that there are at least a few ways to do this. Popbumper Quote Link to comment Share on other sites More sharing options...
ooteedee Posted January 27, 2005 Share Posted January 27, 2005 I have a solution. The quickest and easiest way to finish your speaker? Send your speakers to Michael Hurd! Let him do it. Soounds like they'd come out sweet! Quote Link to comment Share on other sites More sharing options...
analogman Posted January 27, 2005 Share Posted January 27, 2005 ---------------- On 1/27/2005 9:16:39 AM popbumper wrote: Analogman man asked: "Why waste money on spray cans when you're going to sand between coats?" 1) Spray cans are user friendly. They take up little room, need no special equipment/mixing, are inexpensive, less material is wasted, and anyone with a forefinger can use them. 2) Sanding, especially with fine grits, does not remove an appreciable amount of material (as you noted - they SMOOTH rather than CUT), so you are not going to "waste" much anyway. Not sure why you would ask that? Popbumper Michael: This may not be the best "filler", agreed, BUT, once the initial films adhere to the surface and dry, the base material will quit "soaking up" the spray. Primer would probably be the best option. I guess the greater lesson here is that there are at least a few ways to do this. Popbumper ---------------- Good post. I still have a problem with the statement "little material is wasted". That is so untrue, hence the term "overspray". Auto manufacturers spent millions developing systems to limit, capture, and recycle overspray and at the time, as now, they were working in the ultimate environment. Even more sophisticated systems have been developed since. I have never had an overspray problem with brushes or rollers. I understand the obvious virtues of spraying vs. mechanical application of coatings, but nothing changes the fact that it is also the most expensive choice, except with regard to total labor costs. A lot of DIYs have to do some of their work outdoors, few have access to a dedicated booth. I would venture as much as 25% total volume is lost in one way or another to overspray, and unless you're doing your work in Detroit you ain't getting it back. I also made the suggestions I did because cleanup and workspace are less of an issue. Regards, Analogman Quote Link to comment Share on other sites More sharing options...
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