# Water soluble wood glue as MDF primer and much more.



## Johanx3 (Dec 11, 2015)

Hi guys. I was in the need of spray painting some MDF pieces, and concluded that priming its a must before applying your paint, specially in the edges, which is where it shows more signs of porosity. 

What I did was to dilute some water soluble wood glue, using this ratio 1:1, and then applying to the edges you want to seal and prime. I did 3 thin coats, and when dried I notice how the surfaces were actually more harsh, I did not get disappointed to soon, and gave just a little of finishing sand paper. Now the surface was extremely soft and nice, ready to receive the paint. By itself, the sand paper cannot do this, I tried before and it was difficult to get a soft touch.

I have not too much experience with wood glues, and actually always used those wood glues that are waterproof, not sure how good they can perform in this task, I have a gallon of water soluble wood glue (titebond classic) so I used it in first instance. Water soluble wood glues are the cheapest ones in the market, and you can get a lot when buying big quantity as a gallon or a bucket. 

Another good trick I discovered, was that it's so easy play with the viscosity level of this glue, I was in the need where a glue very viscous was more convenient, for example sealing a sealed subwoofer enclosure in its corners, so now the glue does not drip and have more mass, I simply put some glue in a Tupperware or glass and let it seat for hours or days, I mix every 6 hours, because it tends to dry more at its surface, and because all the mix is water soluble, dried sections can be diluted just by the actual amount of water the mix has. Let everything dry until the desired viscosity level.

Its amazing how it dries as a rock, but can be molded or cleaned with a wet rag, I was working inside a subwoofer, and cleaned some messed parts with the wet rag.


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## jorma (Feb 24, 2016)

Are you saying that you used water base glue, as a primer, for paint.?
What will the Solvent/Water in the finish coat do to the "primer" when you apply it.?


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## Johanx3 (Dec 11, 2015)

jorma said:


> Are you saying that you used water base glue, as a primer, for paint.?
> What will the Solvent/Water in the finish coat do to the "primer" when you apply it.?


I got a very fine finish using spray bottle paint on mdf, but surely its not good for using brushes or any other paint, in that case a water proof glue will be more appropriated thing, I have not tried that option.


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## 1acre (Apr 7, 2016)

why didn't you just use a sandable primer?


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## Johanx3 (Dec 11, 2015)

1acre said:


> why didn't you just use a sandable primer?


I have no knowledge/experience about primers, and found how wood glue performs great as primer (next time will use titebond II. which is water resistant, and it's sandable as well). So now I am wondering if a proper primer has advantages vs the method I am using? price? durability, etc? I definitely cannot imagine something being more durable than wood glue, specially titebond 2, that thing once is dried, it's like a hard epoxy resin, and if I am not wrong, wood glues are actually a type of epoxy. So if a proper primer is cheaper than wood glue and in the future I need a lot of it, I can think in giving a try. This time I only needed to prime the edges of some mdf pieces, maybe this is not reliable at big surfaces areas, and primer is required for convenience if cheaper than wood glue.


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## Steve Neul (Sep 2, 2011)

Johanx3 said:


> I have no knowledge/experience about primers, and found how wood glue performs great as primer (next time will use titebond II. which is water resistant, and it's sandable as well). So now I am wondering if a proper primer has advantages vs the method I am using? price? durability, etc? I definitely cannot imagine something being more durable than wood glue, specially titebond 2, that thing once is dried, it's like a hard epoxy resin, and if I am not wrong, wood glues are actually a type of epoxy. So if a proper primer is cheaper than wood glue and in the future I need a lot of it, I can think in giving a try. This time I only needed to prime the edges of some mdf pieces, maybe this is not reliable at big surfaces areas, and primer is required for convenience if cheaper than wood glue.


It's not so much the durability of the glue. It would seal and hold up very well. The problem would come from the topcoat paint adhering to the wood glue. The adhesion would be far better with a primer than glue. In fact I would recommend a primer for a non-porous substrate on the glue before topcoating.


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## 1acre (Apr 7, 2016)

Steve Neul said:


> It's not so much the durability of the glue. It would seal and hold up very well. The problem would come from the topcoat paint adhering to the wood glue. The adhesion would be far better with a primer than glue. In fact I would recommend a primer for a non-porous substrate on the glue before topcoating.


Especially if using a spray paint.


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## Johanx3 (Dec 11, 2015)

Yes, good point, I did a little test before painting my stuff, and found a good adhesion, specially when sanded I think, because with that we create micro porous (invisible to human eye), anyway the bottle says that this glue is sandable and paintable. How much does cost 1 gallon primer? I need it sandable and water proof for convenience for future projects. And please if possible, throw me some good brands, because I can go homedepot and see lots of brands, and have no experience with this.


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## Steve Neul (Sep 2, 2011)

For a latex primer I normally use Kilz II. It can be used for interior or exterior use. A lacquer primer I like is Bushwacker White Lacquer Primer.


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## 1acre (Apr 7, 2016)

for my trim work, where I use a lot of MDF, I use SW's wood and wall primer. It is sandable. Other than that, I have zinsser 1-2-3, which does not sand well. combine that with always have shellac on hand, I have yet to find a need for anything else.


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