PVA Glueing Painted Surfaces? Bad idea?

[sitefive]

Don't have a spray paint gun as don't really have a place where I could afford to use it as it would destroy the room with paint obviously.
maybe in future... however painting with roller weird shape furniture with tons of inner corners sucks and takes ages as well the occasional paint drip...to speed up the process and to get better finish Have decided to paint all the timber before it's cut up in required size pieces & Before it's assembled and glued/screwed together.

However I suppose you can't really glue with PVA painted surfaces together?
Only 1 surface would be painted,the other would be still raw wood you get from cutting the timber to length.
Have not tried to pva glue before together painted surfaces as thought that would be impossible due to paint layer,

Maybe someone smarter can possibly give an idea how could you actually do this?
I Suppose sanding up the painted surface wouldn't really help?
Thanks.

 

[Droogs]

Why not make all the parts and paint it just before assembly and use masking tape to cover gluing surfaces. Let paint dry and remove tape and then glue up

 

[sitefive]

Why not make all the parts and paint it just before assembly and use masking tape to cover gluing surfaces. Let paint dry and remove tape and then glue up

that's actually really clever idea, something I had thought a bit myself but quickly let it fly away for some reason, seems like there's no better way than that.
Oh probably because I thought it would possibly leave paint joining marks, bad experience trying to spray paint some car panels some time ago and using masking tape-left some terrible overlaps and paint borders when masking tape was removed. However should be no issues with that on timber.

 

[lanemaux]

If I may suggest , remove the tape when you finish painting. If you wait until the paint dries , you will not only have trouble removing the tape , you will get paint ridges which are disproportionately difficult to remove. Please don't ask how I know this , I'm still living it down.

 

[petermillard]

However I suppose you can't really glue with PVA painted surfaces together?
I Suppose sanding up the painted surface wouldn't really help?
Thanks.

Pretty much every stick of built-in furniture I've made in the last 10 years has been pre-painted before assembly (high density foam roller, usually a water-based eggshell finish) without any issues, and I always give the mating faces a quick rub over with a bit of abrasive - can't honestly say if it makes a difference, but it feels like it should!

As long as you're also using some kind of mechanical fixing as well as the PVA I can't see there being any problem.

HTH, Pete

 

[ColeyS1]

Head phones in, good ventilation, loud music usually works when I have to do painting. - still a chore, just a little more pleasurable

Coley

 

[ED65]

However I suppose you can't really glue with PVA painted surfaces together?
Only 1 surface would be painted,the other would be still raw wood you get from cutting the timber to length.

Correct, if you glue painted surfaces you're glueing to the paint, not to the wood. And the bond of paint to wood is piddling compared to the bond of wood to wood with a very thin layer of glue in between.

Pre-painting complex assemblies is definitely a good idea though, you just need to protect future glue surfaces from the paint with some tape and you're in business.

 

[blackrodd]

Why not make all the parts and paint it just before assembly and use masking tape to cover gluing surfaces. Let paint dry and remove tape and then glue up

that's actually really clever idea, something I had thought a bit myself but quickly let it fly away for some reason, seems like there's no better way than that.
Oh probably because I thought it would possibly leave paint joining marks, bad experience trying to spray paint some car panels some time ago and using masking tape-left some terrible overlaps and paint borders when masking tape was removed. However should be no issues with that on timber.

You should do more research, To some, All these jobs look simple, they can be, but there are "trick's of the trade".
3M, and others do a "soft edge" masking tape. In it's simplest terms a sponge strip that when used correctly,
saves that sharp edge, sudden stop and start line you spoke of.
You can do it on the cheap, peel an edge of the masking tape back, to end on you're finish line and using the spray gun sympathetically, will have the same "feathered" end.
Ask a car body sprayer to demonstrate or explain more on soft edge masking and also 1/2 gun trigger pressure
for panels, edges and ends.
Regards Rodders

 

[skipdiver]

However I suppose you can't really glue with PVA painted surfaces together?
I Suppose sanding up the painted surface wouldn't really help?
Thanks.

Pretty much every stick of built-in furniture I've made in the last 10 years has been pre-painted before assembly (high density foam roller, usually a water-based eggshell finish) without any issues, and I always give the mating faces a quick rub over with a bit of abrasive - can't honestly say if it makes a difference, but it feels like it should!

As long as you're also using some kind of mechanical fixing as well as the PVA I can't see there being any problem.

HTH, Pete

Pretty much what i was going to say and i've just in the last hour finished a media unit which was all pre painted, apart from all the outer surfaces, which i've just given a final coat to. Still use oil based eggshell myself though, so the house now stinks a bit.

 

[sitefive]

well Decided to test this myself, clamped down loads of samples overnight to test the strength.
-both sides painted
-one side painted, other side raw timber
-one side painted but sanded almost to bare wood, other side raw timber

will post results how much force each joint requires to get them apart once I have some time.

 

[sitefive]

Well I believe the test is over, had about 13-14 different samples from scraps and:
-painted surface glued together with bare wood was just super easy to tear apart, infact you had to use as much force to tear apart a wood+paint joint as just paint+paint - So it's pretty much useless to even use this- to whoever said in their 10years it has been fine- All your joints are still holding together only because of the other fixings not because of the glue.

-Painted surface ( but very lightly sanded) glued together with bare wood- same thing, had no trouble breaking the joints, maybe needed 5% more force
-Painted surface ( but sanded down a lot so you can see the bare wood) actually was pretty tough to break with hands, and when it broke I see the remaining paint chips had come off of a piece)

So seems like if you want to save time Yet still get good strong joints,you have to paint the surface and than sand down the parts where you are going to glue together to almost bare wood.

 

[petermillard]

So it's pretty much useless to even use this- to whoever said in their 10years it has been fine- All your joints are still holding together only because of the other fixings not because of the glue.

No sunshine, read what I wrote; I always abrade the mating surfaces, and always use mechanical fixings (screws plus dominos) so there's plenty of adhesive getting into my joints, thanks. Though just out of interest, so what if they were being held together just by the fixings? I've made plenty of carcasses that were just screwed together simply because they may need to be taken apart and moved sometime - otherwise I make fitted furniture; the only time it's going to move is when it's ripped out and replaced.

Wise to do your own tests - your mileage may vary, and all that - and it'd be good to hear the types of paint and glue you used.

Pete

 

[ColeyS1]

Did you use gloss satin or matt paint in your tests ? I'd imagine satin or matt might stick better than gloss.

Coley

 

[ED65]

well Decided to test this myself

Great little test there! No surprise on the results of course. Paint's hold on wood is nothing compared to glue's.

Did you use gloss satin or matt paint in your tests ? I'd imagine satin or matt might stick better than gloss.

It would, but it doesn't matter much as all that'll do is ensure a better bond to the paint. The weak link in the chain is the bond of the paint to the wood, which is inconsequential. After all masking tape can lift paint from wood sometimes.

 

[sitefive]

Yup not much surprise, satin paint , however it won't really make a difference. I got plenty holding power from the mechanical fixings and they would be enough on their own however I do like to know that glueing things together well gives me another layer of strength to the joint.