Grandpa Bear
Should you paint before assembly then glue up or paint after then cut in your painting.

I mean fenders or bumpers for example. Would you paint them up then fix them for a crisp edge, use masking tape or just be careful and cut in with a small brush.

On the Peterbilt construction tractor and trailor I painted after assembly and fortunately I am pretty good at cutting in, but it takes a while.
What are your preferred methods?
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shedbuddie
I paint before assemble taping areas that are to be glued.
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BadBob
I paint before assembly unless it is all one color.

Masking tape can damage your paint if it is not 100% cured. I might damage it if it is cured.

On bare wood paint will bleed under the tape. 

20181121_194719 Bad Bobs Custom Motors Fenders Masked for Glueing.jpg 
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wwalker47
I paint before I assemble my toys as well. I find that the glue will stick very well on painted pieces. 


-Bill  [comp]

My saw is a DeWalt788
Measure twice; cut once; count fingers after cut
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BadBob
wwalker47 wrote:
I paint before I assemble my toys as well. I find that the glue will stick very well on painted pieces. 




What glue are you using for painted surfaces?



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cynthia lewman
Hi All,

While you can glue the painted surfaces of parts together please keep in mind that the glue bond will not be as strong as gluing bare wood surfaces together. This is especially important when building a rocking or riding toy that's receiving direct force and weight on glued joints. We also recommend using woodworking glue for the strongest bond. Woodworking glue is readily available at your local home improvement store.

Here's what we recommend:

The glue surface of each part is masked when painting the part prior to assembly. We use regular woodworker’s white glue like Elmer’s woodworking glue for assembly with easy to make masks. The mask on basic surfaces is created with masking tape. For example, a fender attached to a body will have masking tape on the glue side as it is primed and painted. An Xacto knife with a number 11 blade is used to cut the surplus tape. It's not necessary that the mask be perfect or cover 100% of the glue surface. Just make sure that most of the glue surface is masked. The edges don't have to be perfect. The mask doesn't have to go to the very edge of the surface.

When applying the glue, apply a thin layer of glue to each glue surface and then scrim the glue with an old credit card or something similar. Make sure the entire surface of each part has a thin layer of glue. Then press the parts together and move then around slightly so the excess glue seeps out around the edges and the bond tightens. Keep a damp cloth handy so you can wipe off the excess glue, then clamp the parts together and let dry. 

Cynthia
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shedbuddie
Hi Cynthia
That's exactly how I do it works great. Thanks
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Rocky
I have a hot glue gun and I find after a while the glue between the pieces dries out and they start to separate.
So I have bought a wood working glue and put the parts together with panel pin and woodworking glue for strength, but sometimes the small pieces split on impact of the pin going in and it destroys my hard work.
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FoxHollowNaturals
cynthia lewman wrote:
Hi All,

While you can glue the painted surfaces of parts together please keep in mind that the glue bond will not be as strong as gluing bare wood surfaces together. This is especially important when building a rocking or riding toy that's receiving direct force and weight on glued joints. We also recommend using woodworking glue for the strongest bond. Woodworking glue is readily available at your local home improvement store.

Here's what we recommend:

The glue surface of each part is masked when painting the part prior to assembly. We use regular woodworker’s white glue like Elmer’s woodworking glue for assembly with easy to make masks. The mask on basic surfaces is created with masking tape. For example, a fender attached to a body will have masking tape on the glue side as it is primed and painted. An Xacto knife with a number 11 blade is used to cut the surplus tape. It's not necessary that the mask be perfect or cover 100% of the glue surface. Just make sure that most of the glue surface is masked. The edges don't have to be perfect. The mask doesn't have to go to the very edge of the surface.

When applying the glue, apply a thin layer of glue to each glue surface and then scrim the glue with an old credit card or something similar. Make sure the entire surface of each part has a thin layer of glue. Then press the parts together and move then around slightly so the excess glue seeps out around the edges and the bond tightens. Keep a damp cloth handy so you can wipe off the excess glue, then clamp the parts together and let dry. 

Cynthia
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FoxHollowNaturals
I paint first, then assemble, then add details, but I never thought about paint impacting the bond; I may have to revisit after reading Cynthia's post above!
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BadBob
It's always good to know your glue and how it works both shot and long term. Wood glue on wood properly applied is stronger than the wood.  It will work on most porous surfaces to some extent because it can soak into the material and make a mechanical bond. Paper, which is wood fibers, will work great with wood glues. As an experiment put some wood glue on a glossy nonporous surface lie the shinny side of aluminum foil for example. Once cured, it will pop or peal right off.

If you glue painted surfaces together with wood glue, it's like a chain being only as strong as its weakest link. The paint will bond well to the wood, but the glue will not bond well to the paint. Depending on the paint used, putting the parts together with wet paint might work better.
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Frankg
Sometimes for tiny areas I use Cyanoacrylate like Gorilla glue. I have not had a problem applying on painted surfaces. However I try to use the bare wood area if I can.
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BadBob
I don't use Cyanoacrylate for toys.  It is expensive and has a short shelf life — less than a year in my environment. To get the best bond, the wood needs to be very clean, and you need to apply accelerators. The bonds are not near as strong as PVA glues and deteriorates rather fast. In my experience, it just doesn't hold up. I expect my toys to be heirlooms. That's probably wishful thinking, but just in case I don't want them to fall apart.  

PVA wood glues can and do last for many years, have a long shelf life, the bond lasts for years, and the joint is stronger than the wood.
 
I also use epoxy, but only for extraordinary things like gap filling or bonding dissimilar materials.

Cyanoacrylate is suitable for gluing a cut closed so you can keep working without getting blood on your toys.
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Martin L
I do not paint the areas where I am going to apply glue as I do prefer to paint before assembly. The glue I use is Titebond 3 as it is water proof and it is food safe, this may seem unusual to many but I do get people asking if there is any problem with children putting the toy in their mouth.
 The way I approach the project is to mark where the parts are to be glued then when painting the parts I allow a 1mm encroachment over that line to save having to touch up afterwards.  If it is a timber finish with a lacquer coat I complete the assembly then spray apply the finish, more often than not I will paint the tyres black to make them stand out.
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BadBob
Here is one car I did without making with blue painters tape. It worked, but it made painting the body difficult. I traced the outline of the fender on the side of the car body and made sure I painted over the lines. If I use tape, I put tape on the car body then trim the tape about 1/8-inch inside the line. It's much easier to paint this way. Making is the only way to do it if I'm spraying the paint.
 
20180314_205314_HDR Handmade Wooden Toy Car Bad Bobs Custom Motors Gre.jpg 
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