Laminate over mdf

ani_101

I have a short stack about 6.75 inches (9 layers) of stacked mdf for a smallish speaker. I want to seal the layers and sand and then laminate over the layers, so that the layers are smoothed and not visible. Then either paint or veneer over the laminate. The mdf face would not be laminated, just the sides where they are stacked.

I am hoping to use heat lock adhesive for the laminate and zinser bin sanding sealer.

Questions
1. Can I use sanding sealer, sand and then Lanie over it using heat lock adhesive?
2. Should I seal the inside of the layers, this of course needs to be done before I put the end cap face layer mdf on. Can I use some sort of rubber coating on the inside like flex seal or red seal?
3. Would you suggest something else?

ani_101

It is mdf, and not Baltic birch and most of the layers are glued, except the end caps, so I can still access the inside. Mdf is a lot easier to route and sand, but more problematic with moisture.... 

dcibel

Zinsser BIN and SealCoat are shellac based products. Shellac is great and my preferred sanding sealer, but it doesn't withstand heat, so if you're going to use an iron on method for the veneer I would go for a different sealer. I'm not experienced wit Heat Lock product, but it may be a good sealer on it's own, in which case you may be able to use the shellac sealer on all surfaces except where the veneer is being installed.

From the Sealcoat technical data sheet:

"SealCoat is not recommended for use in areas where surface heat exceeds 160°F (71°C)"

To prevent swelling and shrinkage of the MDF over the seasons with relative humidity changes, I would seal inside and out. I started doing this on recent projects due to protruding seams on older projects that were perfect when originally assembled and finished. My recent builds have held up better so far with only very minor creepage on the seams.

Wolf

Ani- sounds like you need to pick up some West Systems epoxy. I recently started using it (with the metering pumps), and it is really great to use. I've used the basic clear resin with the clear hardener. That will seal the MDF very well, and it will not give afterwards. You'd have to look up the heat specs to see if it will stand the iron-on methods, but my guess is it will for the limited amount of applied time. Nick uses it on his cabs before paint or veneer, but I don't know if he bags it or uses the iron on methods.

ani_101

Sounds good. And thanks for the warning on the heat tolerance for shellac.

Can I use epoxy to stick the laminate? Else I might need to go for double thick layer of veneer to prevent telegraphing.

Wolf

With epoxy, it won't telegraph. It won't move. Yes you can glue it on with it.

ani_101

What's a metered pump? The searches for West system epoxy is coming up with 105 kit with yellow colored pump and hardener... 

dcibel

First search result for "west coast epoxy metered pump".

https://www.westsystem.com/the-105-system/metering-pumps/

jhollander

I iron on veneer (with PVA glue) over BIN without issues.  I do coat both the mdf and veneer with PVA glue.

The proposed assembly sound problematic as the plastic laminate going to telegraph at the edges. If you add another layer over the laminate is going to make the edge line look wider.

I'd skip the laminate and harden off the mdf with lacquer sanding sealer flowed by multiple coats of BIN shellac based.

ani_101

Thought would post some image. This is showing from the top (which will be the sides of the speakers, where the end caps will go). The sides which are the layered mdf will be the baffle and back. Ultimate aim is to paint the boxes, but if the paint does not look good then I might veneer over it. I am neither good at painting or veneering...

Trying to expoxy in winter may not be feasible... 
So any other suggestions? 

ani_101

@jhollander do you have any suggestion or brand for lacquer sanding sealer? Would it get absorbed into the mdf and harden it? Haven't used lacquer sealer...

Wolf

Yes- epoxy should be done in 50+* weather.

jhollander

I have used Behlens and Deft.  Other than the bad MDF I got from Lowes, the lacquer sanding sealer etches and stop seals the mdf for the shellac sealer.  There's probably no end to the MDF soaking up the lacquer, as I recall I did 3 or 4 brushed on soaking coats then used BIN on top. I've also used Seal coat on top.

ani_101

Another question. So I have been looking at sealers and came across vinyl sealer, and it send to be used before applying lacquer. Lawyer would get soaked up whereas vinyl sealer has higher solids and wouldn't get soaked up as much.... 

Thoughts? Vinyl then lacquer or just soak mdf in laquer? Vinyl also has a harder surface.

PWRRYD

While laquer looks amazing on nice hardwood, it is some terribly stinky stuff that I would never consider using to seal MDF.  I have found that Bins 123 shellac works great sealing MDF before applying veneer.  But I've only used paper backed veneer with solvent based contact cement.  I don't know how it would work with water based contact cement or iron on with PVA.

ani_101

John H mentioned iron on with Bin should be fine. 

PWRRYD

True, and the old saying is "shellac goes over anything and anything goes over shellac".

jhollander

Vinyl sealer is on my list to try.  Most pro cabinet shops use a vinyl sealers for painted cabinets.  Sourcing was a problem.  If you have a source please share, I haven't looked for over a year.

Craig we were talking about lacquer sanding sealer
https://www.amazon.com/d/Wood-Stains/Minwax-154000000-Lacquer-Sanding-Sealer/B0019C2LXC
https://www.truevalue.com/lacquer-sanding-sealer-1-qt
https://www.woodworkingshop.com/product/df01504/

ani_101

There are some for sealing guitars, don't have any expressive with it, but it came up in searches.