With the use of the duratex, I just was commenting on the fact that it does not lay flat (depending on how you apply it), and it's a little bit harder to sand than some others. It's really tough stuff. It was easier for me to sand through epoxy than the duratex.
Your speakers look great. I'm curious if there was a reason you used Particle board other then the low cost? I think if a cabinet is properly braced solid wood like oak doesn't have much of/if any issue with resonances.
@ugly_woofer said:
Super glue and epoxy both will help hide the seems
Use superglue as the holding glue or fill in the seams with it? Have a writeup?
If you use CA glue or epoxy for the joining adhesive, either one will provide a glue joint with less shrinkage than PVA glue, but I have used both to help stabilize the PVA glue joints in MDF by soaking the whole area. It's surprising how much MDF will absorb on the uncut side, and forget about the end cut, it's a sponge.
OK, so here is a list of things I have discovered minimize or eliminate seams broadcasting.
First, seams are the result of disparity in expansion rates due to absorbtion. After running the trim bit around an oversize panel, set a straight edge on it. After applying the first coat of anything the MDF will soak up, apply the same straight edge. It will be reasonably obvious at that point.
Do not clamp the living shit out of things unless it is permanent. Meaning, clamp the shit out of it and still use brad nails or screws. Personally, I use no more pressure than I can apply by hand and let the brads take over from there. As the PVA shrinks, the panels have nowhere to go. On the surface it may appear the seams are bigger, but they really take filler better that way.
Use a high quality filler, whether that is black lid Elmers or body filler. Feather it on from seams to panel and sand it smooth. You will take quite a bit of it off.
Use a glaze over things. Same technique, but no need to be aggressive if you did the filler right.
Block the glaze and look for the fill lines - if need be apply a second coat of glaze. Lather, rinse, repeat.
If painting, use a high build primer for first coat and wait a helluva long time for it to cure. Stick your beak directly on the surface and if it smells like paint - it is still curing and therefore still shrinking. When it is cured, you will still see slight broadcasting of the seams. If your primer is thick enough - block sand them out. They won't be coming back. If it doesn't generate a very fine powder as you sand or if there is any buildup on the paper that doesn't readily knock off, you fucked up and went after it too soon and will have to likely re-apply the primer. So be patient. Build another set of cabinets in the meantime. Go for a vacation. Anything to keep your mind off of the drying primer.
If you are applying Duratex, apply first coat only around the seams. Good heavy build. When it cures completely (about a week weather dependent), block sand it all the way down. The seams will be very visible since they will be filled with duratex.
Apply full second coat. Let cure and inspect.
No need to recoat 14 times - after first full coat of Duratex, block sand just the seams. Good time to knock back any bumps or runs as well.
Apply top coat as normal.
120 grit is good enough for most of the above, although if you are looking for a painted piano finish you may want to go to 220 on the primer. You will have little curlycues broadcast through paint otherwise. Nobody wants to look at that shit lol.
Other considerations: if using a RO or DA, take it easy. Don't tip sander on the edge to grind the hell out of things. Always remember that the flat side will have material removed at a different rate than the end "grain", exacerbating things. This is why I recommend block sanding so much. Tedious? Fuck yes - which is why first chance I got I stopped helping the old man do body work. Effective? Ask any body man the key to a smooth finish.
Another thing to be aware of is scalloping the flat panels. A lot of guys are afraid to run the sander too far over the edge so the center of the panel effectively gets 2X the sander time leading to a scalloped panel. This can emphasize the seams as well. Again, block sanding is the key. I still screw this up to this day.
There is a DIY'er I know who applies a water based primer very heavily on the end seams, and lets it expand deliberately. He then runs a trim bit around things and I guess it works pretty well for seam hiding.
This is a bad picture, but it shows how much the untreated MDF soaks up the primer. The edges were soaked with epoxy and block sanded flat before applying the primer. Keep in mind that I used 2k primer which is catalyzed and sets quickly, so there wasn't much time to soak in and yet it's clearly visible how much the treated areas are standing proud of the untreated. I personally prefer to sand to 400 or 600 pre-paint.
That's a camera trick. It's probably about 10 thousandths of an inch. If you're talking about the side "rails", they are about 1/4", that's how Dan designed the portals.
@kenrhodes said:
Steve, most sanding sealers are dewaxed shellac. Usually shellac is a little cheaper.
Hey, Ken - I was just throwing my two cents-in.
I use water based products as much as possible for the easy clean-up low fire hazard/fumes and it swells the wood as it absorbs and hardens the substrate - two heavy coats and sand flat and it holds up pretty well with finishes applied.
Not sure if water based sealer contains shellac or not - I'm no expert.
ASIDE > While we are on this subject; I have some old Acculab cabinets that have a vinyl veneer on them and am wondering how I can apply Duratex over them and the edges need a slight round-over (Cabinets are particle board) to clean up the frayed edges - any suggestions, guys?
Sorry for the hijack - just thought this was on topic at the moment.
Comments
A little off topic, if duratec is sanded smooth, can it be painted and will it hide the seams?
Yes it can. With a lot of elbow grease.
InDIYana Event Website
Wolfy's Photobucket
Super glue and epoxy both will help hide the seems
Agreed!
InDIYana Event Website
Wolfy's Photobucket
Use superglue as the holding glue or fill in the seams with it? Have a writeup?
No more elbow grease than any other method. There are some secrets to hiding seams.
With the use of the duratex, I just was commenting on the fact that it does not lay flat (depending on how you apply it), and it's a little bit harder to sand than some others. It's really tough stuff. It was easier for me to sand through epoxy than the duratex.
InDIYana Event Website
Wolfy's Photobucket
Your speakers look great. I'm curious if there was a reason you used Particle board other then the low cost? I think if a cabinet is properly braced solid wood like oak doesn't have much of/if any issue with resonances.
Only because it was super cheap shelving material.
Locally, lumber has dropped a lot but still higher than it was a few years ago.
If you use CA glue or epoxy for the joining adhesive, either one will provide a glue joint with less shrinkage than PVA glue, but I have used both to help stabilize the PVA glue joints in MDF by soaking the whole area. It's surprising how much MDF will absorb on the uncut side, and forget about the end cut, it's a sponge.
You might be surprised what a couple of coats of shellac will do.
I just use 2 heavy coats of sanding sealer.
Steve, most sanding sealers are dewaxed shellac. Usually shellac is a little cheaper.
OK, so here is a list of things I have discovered minimize or eliminate seams broadcasting.
First, seams are the result of disparity in expansion rates due to absorbtion. After running the trim bit around an oversize panel, set a straight edge on it. After applying the first coat of anything the MDF will soak up, apply the same straight edge. It will be reasonably obvious at that point.
120 grit is good enough for most of the above, although if you are looking for a painted piano finish you may want to go to 220 on the primer. You will have little curlycues broadcast through paint otherwise. Nobody wants to look at that shit lol.
Other considerations: if using a RO or DA, take it easy. Don't tip sander on the edge to grind the hell out of things. Always remember that the flat side will have material removed at a different rate than the end "grain", exacerbating things. This is why I recommend block sanding so much. Tedious? Fuck yes - which is why first chance I got I stopped helping the old man do body work. Effective? Ask any body man the key to a smooth finish.
Another thing to be aware of is scalloping the flat panels. A lot of guys are afraid to run the sander too far over the edge so the center of the panel effectively gets 2X the sander time leading to a scalloped panel. This can emphasize the seams as well. Again, block sanding is the key. I still screw this up to this day.
There is a DIY'er I know who applies a water based primer very heavily on the end seams, and lets it expand deliberately. He then runs a trim bit around things and I guess it works pretty well for seam hiding.
Good info JR. I think I'm guilty of always tightening my clamps way too tight during glue up. If a little is good, a lot is way better LOL!
One hijack, then I'm done, I promise.
The importance of block sanding can be seen in this picture:
Heavily edited of course. Regular powered sander would not reveal that nearly as nice. Next coat of the good stuff will suffice.
If I was going to paint them, this is where I would sand edges and roundovers.
This is a bad picture, but it shows how much the untreated MDF soaks up the primer. The edges were soaked with epoxy and block sanded flat before applying the primer. Keep in mind that I used 2k primer which is catalyzed and sets quickly, so there wasn't much time to soak in and yet it's clearly visible how much the treated areas are standing proud of the untreated. I personally prefer to sand to 400 or 600 pre-paint.
They look like they are standing proud by about a quarter inch or more!
That's a camera trick. It's probably about 10 thousandths of an inch. If you're talking about the side "rails", they are about 1/4", that's how Dan designed the portals.
Hey, Ken - I was just throwing my two cents-in.
I use water based products as much as possible for the easy clean-up low fire hazard/fumes and it swells the wood as it absorbs and hardens the substrate - two heavy coats and sand flat and it holds up pretty well with finishes applied.
Not sure if water based sealer contains shellac or not - I'm no expert.
ASIDE > While we are on this subject; I have some old Acculab cabinets that have a vinyl veneer on them and am wondering how I can apply Duratex over them and the edges need a slight round-over (Cabinets are particle board) to clean up the frayed edges - any suggestions, guys?
Sorry for the hijack - just thought this was on topic at the moment.
Thanks.
Never knew there was water based sanding sealer.
It's not, shellac is alcohol based.
InDIYana Event Website
Wolfy's Photobucket
Ben, check this out:
https://www.lowes.com/pd/Minwax-Water-based-Sanding-Sealer-Actual-Net-Contents-32-fl-oz/999914203