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Re: Best methods for finishing MDF
Good observation. To bad you didn't seal the end joints before you put the box together. From my experiments so far any liquid will expand MDF. I assume the glue isn't "liquid" proof so when it is soften it allows the compressed MDF to decompress.
I had thought about the wood glue joint being weaker because it can't absorb into the wood as much. I suppose epoxy would cure that problem. I was in hopes of staying away from epoxy. I was also thinking about a method to rough up the surface after sealing with the thinned resin. Some kind of indents, deep scratch lines or small perforations along the end grain. Some kind of simple tool similar to how a wall paper tool puts the perforations in the paper for water to get behind.
Dave
Originally posted by williamrschneider
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Yes, there's a seam on the other side. If the light/dark junction of the doorway reflected in the background doesn't "break" across the seam, you can't see it. The two-veneer techniques has helped, but not eliminated the telegraphing problem. I had thought that a ~1/16" thick sandwich of veneer and glue lines would help more, but I guess not.
Anything's worth a try. All we can do is experiment and report the results. One issue with a coating like that is that a different adhesive would be better than wood glue. I once read an old US Forestry service bulletin about how an application of shellac greatly reduced the effectiveness of wood glue.
Before I knew that, I once applied a generous helping of shellac over some assembled cabinets before veneering. It also swells the MDF, and here's visible proof (showing the location of the biscuits beneath after some sanding) that it differentially swells areas of the MDF depending on whether glue in the biscuit slots is preventing deep absorbtion ...
Even with the heavy application of shellac soaked into the end grain, this pair of speakers, once veneered, also telegraphs seams through the veneer. These were built in dry weather, so the seams show in humid summer conditions and disappear in winter. My conclusion was that shellac after assembly (but before veneer) didn't work.
Anything's worth a try. All we can do is experiment and report the results. One issue with a coating like that is that a different adhesive would be better than wood glue. I once read an old US Forestry service bulletin about how an application of shellac greatly reduced the effectiveness of wood glue.
Before I knew that, I once applied a generous helping of shellac over some assembled cabinets before veneering. It also swells the MDF, and here's visible proof (showing the location of the biscuits beneath after some sanding) that it differentially swells areas of the MDF depending on whether glue in the biscuit slots is preventing deep absorbtion ...
Even with the heavy application of shellac soaked into the end grain, this pair of speakers, once veneered, also telegraphs seams through the veneer. These were built in dry weather, so the seams show in humid summer conditions and disappear in winter. My conclusion was that shellac after assembly (but before veneer) didn't work.
I had thought about the wood glue joint being weaker because it can't absorb into the wood as much. I suppose epoxy would cure that problem. I was in hopes of staying away from epoxy. I was also thinking about a method to rough up the surface after sealing with the thinned resin. Some kind of indents, deep scratch lines or small perforations along the end grain. Some kind of simple tool similar to how a wall paper tool puts the perforations in the paper for water to get behind.
Dave
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