Liquid glues (like Weld On)?

Sluis Van Shipyards

Legendary Member
I watched a Tested video where Adam was showing how to do paneling for a scifi model. Several times he mentioned using Weld On and said ILM guys had used it. I've also heard it's very toxic. I can't see anyone using it if it was THAT bad. So is it, or do they mean it's bad if you sat there huffing fumes all day, not just using it for minutes at a time? Also I've never had good luck with liquid glues, like the stuff Plastruct sells. My parts usually lift right off. So say you're gluing a flat piece of styrene, say 1"x1", how far does the liquid glue get sucked under it to bond? The times I've used it, it maybe flowed in 1/8".
 

star-art

Sr Member
The manufacturer of Weld-On solvents recommends an air-supplied respirator, so that's how toxic it is. Working outside is a bare minimum. If you can smell it, it's harmful. Don't breathe the fumes! Even for a few seconds.

Liquid glues tend to be very "hot" so they evaporate quickly. You really need the right glue for the plastic you're using. If you try to bond different materials together, it may or may not work. For example, I've had difficulty gluing certain parts to styrene. These were likely ABS. They would stick initially but pop off easily. Turns out I needed a special solvent (like Plastruct Plastic-Weld) that can cross-bond acrylic, styrene, ABS, and butyrate.

As for flat pats, "capillary action" will draw the liquid underneath the edges, but only a little ways. The amount depends on the fit. The tighter the fit, the less distance it will travel. But, you have to be careful because too much solvent will cause wrinkles in your thin styrene. These might not appear until hours or even days later. So, for thin panels, it might be best to use a non-solvent glue like CA or epoxy.

But, I've had epoxy bonds fail with styrene so I've decided it's not suitable for critical or high-stress applications.
 

swgeek

Sr Member
He's using Weld -On 3, or 4. I prefer 3 but it's hard to get in California. It will glue styrene parts permanently and quickly and yes it is very toxic. If you wear a respirator and gloves you'll be fine.
 

star-art

Sr Member
I don't want to sound harsh or extreme but please hear me on this:

This is an industrial solvent that is not to be taken likely. It is not suitable for home or non-professional use without proper precautions and equipment.

Again, this stuff is so noxious the manufacturer recommends an AIR-SUPPLIED respirator. That's one with its own external air supply. In other words, a regular paint or chemical respirator will not offer enough protection. If you can smell the fumes, they are doing harm.

I tried using a regular chemical respirator, plus a fan to blow air across my work area, but I could still smell the fumes and they made me sick. If you don't have the proper safety equipment, working outside is the only safe alternative. You should NEVER use this stuff indoors.

Since I work with it a lot (and have for many years) I designed and built a custom ventilated work booth similar to the kind you might find in an industrial setting. This pulls air across my work surface and exhausts it directly outside. It's the only safe way to work with this stuff indoors.
 

Pro Mod

Well-Known Member
RPF PREMIUM MEMBER
Product such as Tamiya Extra Thin Cement or Humbrol Liquid Poly types are better for thinner styrene sheet as they're not as aggressive and may reduce the wrinkling that star-art mentioned.

Any of the liquids will only capillary in so far unless you apply a huge amount.
On larger panels I first apply a few drops to the surface, drop the panel on top and then brush more around the edges once I'm happy with its position.

Adam probably uses Weld-On because they used it as a universal solvent for plastics at ILM and he knows it works.

When I trained as a modelmaker we used Dichloromethane all the time (still do) for bonding acrylics and ABS but it's not great for everything!
 

Duncanator

Sr Member
We used Weld-On 3 & 4 at ILM (along with lots of other glues as well) because they were good for styrene and acrylic - which is what we used a lot. For ABS, urethane or other materials, you’d want to use another adhesive.

Yes! It is bad for you. All solvent glues and paints are bad for you. We used it because it worked, not because it was healthy.

We tried to have as much ventilation as we could get to minimize breathing fumes - and just cuz you can’t smell them, or they don’t smell bad doesn’t mean the fumes aren’t there. Use wisely.
 

star-art

Sr Member
If you have a small spray booth that vents outside, you might be able to use these solvents more safely at home. It depends on how much air it moves, of course, but if you can keep the work (and glue) between you and the booth, chances are most of the fumes will be drawn away and sent outside.

Another thing that helps is a Menda Pump. These dispensers can keep the solvent from evaporating as quickly by dispensing only tiny amounts at a time. I use a syringe applicator to transfer the liquid from the can to the pump so the lid is off for only a few moments. Then, I use a natural-hair artist's brush to apply the solvent.


 

Sluis Van Shipyards

Legendary Member
Ok so I guess I'll skip that one for now! Has anyone tried using lacquer thinner? I remember someone in the late 90s sent in pictures to my old website of an Interdictor Star Destroyer scratchbuilt from styrene and he said he glued it together with lacquer thinner.
 

Duncanator

Sr Member
Ok so I guess I'll skip that one for now! Has anyone tried using lacquer thinner? I remember someone in the late 90s sent in pictures to my old website of an Interdictor Star Destroyer scratchbuilt from styrene and he said he glued it together with lacquer thinner.
Well, lacquer thinner is also bad for you.:confused:

Really any solvent based adhesive you use has some level of toxicity. But they are all ok to use so long as you are smart about how you do it.
Having adequate ventilation is the number one priority.
If you think about, any chemical that is able to dissolve plastic can't be good for you.
 

Sluis Van Shipyards

Legendary Member
Well I mean there's "air supply required" and then there's "Just have adequate ventilation" :lol: I think the amount of time I'm using any of them probably isn't enough to do much damage though.
 

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