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Has anyone mastered hiding joint lines?

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  • #16
    Re: Has anyone mastered hiding joint lines?

    I'm still learning...

    I do like water bornes for their convenience.
    Target finishes for spray and Varathane for brushing. With acrylic artist paint for color or one of the better acrylics like Sherwin Williams.

    Good old NC lacquer when I feel up to dealing with the solvents. It is the spray finishers dream finish IMO. Fast and easy and nothing else looks quite like it, colored or clear, in any glosss level you might want.

    Oil based varnishes I like P&L 39 when I need something pale in color but it's geting harder to find, Waterlox for a deeper amber. Minwax and Olympic are also very good in their own ways, as is Varathane solvent based varnish.

    Shellac, both canned and flakes for finish or sealer (only dewaxed SealCoat when used for a sealer under other finishes).

    Killz for a universal primer that sands fairly easily.

    When I need it, epoxy. I prefer System 3 with the slow set hardener as it's very thin. Have to switch to fast hardener now that the weather is bad. Other brands like West Systems work equally well. Can be tinted or pigmented and can be topcoated with almost anything. But it is no fun to work with and is relatively expensive.

    For other things I like oils, waxes and shellac in a never ending variety of combinations. Pure Tung oil is a fine finish itself. Walnut, too. Sometimes mixed to alter color/drying. I avoid linseed oil except when needed, which means when I'm making paint or something where it excels it some way as a plasticizer or grain enhancer for example.
    ~99%
    Make me an angel that flies from Montgomery
    Make me a poster of an old rodeo
    Just give me one thing that I can hold on to
    To believe in this livin' is just a hard way to go

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    • #17
      Re: Has anyone mastered hiding joint lines?

      Here is a link to a long thread I started about the subject a few years ago when I came up with the trench method that is in my signature. Post 36 showes some of the samples I tested. I have a whole shelf of them. The trench was the only one I found to work. I did not try West System Epoxy which probably would work. I would take Bobs advice. He's a world book of knowledge.
      http://techtalk.parts-express.com/sh...-finishing-MDF

      Dave
      http://www.pellegreneacoustics.com/

      Trench Seam Method for MDF
      https://picasaweb.google.com/101632266659473725850

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      • #18
        Re: Has anyone mastered hiding joint lines?

        My father did body work on cars for 36 years I discovered that it’s not so much the product being used but the method that its applied and how is sanded afterwards. It holds the same for the wood world. I have a few projects (not all speakers) that I was able to make pretty perfect with nothing more than bondo. I find people like to sand it down the line and MDF after it’s been applied and that’s never going to hide the line. Leaving the correct amount of material is the key.

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        • #19
          Re: Has anyone mastered hiding joint lines?

          I'm with WoodCock. I don't think the product is that crucial as long as the method is sound. I have found that slightly trenching the seam and filling it in with good ol' drywall putty (mud) works very well. I use the 'fine' grade of putty. Remember, this stuff is used all the time in homes and businesses. Assuming a qualified painter did the work, I have never seen any seams or joints after this is applied and painted over. And houses and businesses last for years of environmental changes. I know that mdf is a different material than drywall, but the method still works. The lesson I was taught in painting is 'if you can feel it, it's gonna show'. Has held true so far.
          If dynamite was dangerous, do you think they'd sell it to an idiot like me?

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          • #20
            Re: Has anyone mastered hiding joint lines?

            FWIW, the fool proof method I've found is to simply build your cabinets with as many seams as possible hidden and the rest grouped together. I then put a piece of 1/8" MDF on those sides where the seams are grouped which are usually top, bottom and back. I use 1/2" & 3/4" MDF for the front baffle with the 3/4" piece hidden and the 1/2" flushed to the front. The 1/8" seam is very easy to hide and the 1/2" seams on the front edges seem easier to hide than 3/4" for some reason.

            I've done a lot of gloss black painted speakers and this is the easiest way I've found to eliminate most if not all of the seam issues.

            HTH

            Jim

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            • #21
              Re: Has anyone mastered hiding joint lines?

              If someone would only make an MDF veneer......
              Audiophiles listen to the equipment, not the music.

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              • #22
                Re: Has anyone mastered hiding joint lines?

                It's out there. Just a matter of where to get it. Here's a link

                http://www.winwood-products.com/eng/...f_supplies.htm

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                • #23
                  Re: Has anyone mastered hiding joint lines?

                  Originally posted by richard t View Post
                  It's out there. Just a matter of where to get it. Here's a link

                  http://www.winwood-products.com/eng/...f_supplies.htm
                  I was thinking of an actual veneer made of mdf that could be applied over an enclosure that would hide all seams. I've tried mitering the pre-veneered panels without much success. But that is a product of my ability & the accuracy of my equipment.....
                  Audiophiles listen to the equipment, not the music.

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                  • #24
                    Re: Has anyone mastered hiding joint lines?

                    My mistake.
                    The thinnest mdf I've seen is 1/4 inch.
                    Not sure if that would work for you.

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                    • #25
                      Re: Has anyone mastered hiding joint lines?

                      what about 1/8" HDF / Masonite?

                      i might try using that in my next build - for bending purposes though, not seam issues.

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                      • #26
                        Re: Has anyone mastered hiding joint lines?

                        Originally posted by bobbarkto View Post

                        As to seams showing.. Much depends on personal expectatons and the quality of the finish and the observers tolerance for defects.
                        A very good high gloss finish, in a dark color, will show the seams without some attention beyond carefull joinery, sanding and finishing. Unless the relative humidity never varies for any length of time from the time of finishing.

                        In my testing I observed that;
                        Most adhesives do not expand or contract at the same rate as the mdf. They remain relatively stable while the mdf increases or decreases in size around the glue adhered joint.
                        As mdf shrinks and expands with changes in moisture content (from moisture in the air) the glue line remains fixed relative to the movement of the flat panel. This leaves a small dip or a slight bulge at the glue line. This defective appearance extends outward some distance in at first a sharply decreasing then more gradual slope. The amount the slope extended varied but was inconsequential compared to the sharp rise or fall very close to the glue line.
                        Further, the difference in hardness between the adhesive and the mdf caused some resulting irregularity in the surface immediately around and on the glue line after sanding. This was only alleviated by surface coating the area and further sanding. This might be a contributing factor but I have not researched it further. It was a well known phenomenon to me beore I started my observations.

                        Here is an image, taken from 2 directions, of the corner of a cabinet I've had sitting around a long time (please excuse the dust!).



                        After thorough sanding to as level as possible a coat of shellacwas applied on the ends/edges, fine sanded and followed by 1 coat of vinyl sealer, then 3-4 coats of lacquer primer/surfacer sanded level, another coat of primer lightly sanded and then many coats of gloss black lacquer, which was sanded and polished to a high gloss. The finish was applied during a period of relaively low humidity. It showed no seams when in a high gloss state. Shortly after finishing the weather turned more humid and the seams showed.
                        I began to sand back, hencce the dull surface, and stopped when the seam almost disappeared. It always remains visible due the differing gloss level relative to the rest of the surface.

                        You can probably see the bright glossy line in the top image, along the right edge extending up and slightly left toward the top of the image. There is an identical seam along the edge in the foreground that is invisible in this image to my eye.
                        At most other angles the visible seam is invisble as in the lower image.
                        Bob, the picture you are showing looks like sunken glue joint. Isn't that correctable with delayed sanding or epoxy glues?
                        John H

                        Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

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                        • #27
                          Re: Has anyone mastered hiding joint lines?

                          Originally posted by richard t View Post
                          My mistake.
                          The thinnest mdf I've seen is 1/4 inch.
                          Not sure if that would work for you.
                          You can order 1/8" MDF from a hardwoods store. Most don't stock it. Liberty Hardwoods in Des Moines, Kansas City and Omaha does stock it. It's cheap too at about $6.00 a 4x8 sheet.

                          Jim

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                          • #28
                            Re: Has anyone mastered hiding joint lines?

                            Originally posted by bobbarkto View Post
                            Shellac is good to almost great at ~40% for plain shellac to ~70% for some pigmented shellac (eg: Killz or BIN).
                            I actually have some Killz here, but I got the cheap kind. There were two different kinds, the only difference I could see in the description was that the expensive kind hides stains. I didn't have any stains on my new speaker boxes so I got the cheaper one. Is it ok or do I need the other kind? Also it's white, should I get pigmented instead to increase vapor resistance?

                            So it sounds like 2 part epoxy or maybe a nice lacquer is the way to go. Can you recommend a brand name and maybe a couple of stores that carry this stuff? Also vinyl sealer.
                            Don't even try
                            to sort out the lies
                            it's worse to try to understand.

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                            • #29
                              Re: Has anyone mastered hiding joint lines?

                              The white is the pigment. Plain shellac is clear (or amber or garnet), i.e. transparent.

                              Originally posted by diy speaker guy View Post
                              I actually have some Killz here, but I got the cheap kind. There were two different kinds, the only difference I could see in the description was that the expensive kind hides stains. I didn't have any stains on my new speaker boxes so I got the cheaper one. Is it ok or do I need the other kind? Also it's white, should I get pigmented instead to increase vapor resistance?

                              So it sounds like 2 part epoxy or maybe a nice lacquer is the way to go. Can you recommend a brand name and maybe a couple of stores that carry this stuff? Also vinyl sealer.
                              I was so much older then, I'm younger than that now.
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                              LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

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                              • #30
                                Re: Has anyone mastered hiding joint lines?

                                Do you think that the majority of the humidity issues are caused by humidity penetrating the wood from the untreated (inside of a speaker if using speaker as example)? I don't think ive seen a build thread where the insides were sealed, but perhaps if this were done so no bare wood was exposed then the effects would be minmized. I have thought about spraying some primer sealer through the woofer cutouts on my finished speakers; I think I could reach every interior spot with a spray can and the reach of my arm.

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