Ever pick up like a. Maybe a phone case or a toy and think, this could be so much better if it wasn't so blah. That's where paint comes in. We're going deep on painting injection molded products.
It's amazing what paint can do.
We've got excerpts from a guide on painting these products.
Okay.
By the end, you'll be turning those boring plastic pieces into works of art.
Nice.
You'll know the how to Andy the why.
We'll break it all down.
First up, surface prep. Right, like prepping a canvas. You wouldn't start painting on a dusty canvas.
Definitely not. This guide says we gotta clean the plastic with isopropyl alcohol.
Oh, so like, just get all that grime off first.
Yeah, you'd be surprised how much oil and dirt builds up. And then the paint won't stick. Right.
It's a good cleaning before we even start.
Exactly.
But the guide says there's more.
Yeah, sanding.
We gotta sand the surface too.
Oh, yeah. With sandpaper grit levels between 240 and 800.
So we're scratching it up on purpose?
You got it. Sounds counterintuitive, but those tiny scratches actually help the paint stick better. More surface area for the paint to grab onto.
So roughing it up creates a stronger bond.
Think of it like this. A perfectly smooth surface. Nothing for the paint to grip. The scratches are like little anchors for the paint.
Okay, that makes sense. Now, what about those tricky plastics like polypropylene and polyethylene? Yeah, those are hard to paint, right?
Yeah, they have low surface energy.
What's that mean?
Paint just doesn't want to stick. This guide suggests some chemical treatments like Corona treatment.
Corona treatment?
It changes the surface energy, makes it more receptive to the paint.
What's it actually doing to the plastic?
It's like waking up. The surface uses an electrical discharge to make it more reactive, like adding little handles for the paint to grab onto. Or you can use a primer too.
So it's like with plastics, prepping is even more important.
Absolutely. Crucial for good results.
Okay. Surface prepped paint. But how do we choose with all the types out there?
Well, first you gotta know what kind of plastic you're working with. Ah, so they're not all created equal.
Nope. They all have different properties. And not all paints work well with every plastic.
So you can't just grab any old can.
No, you gotta do your research first.
Okay.
For example, ABS plastic is pretty easy. Acrylic or polyurethane paints work well on it.
Hmm. But are there any? Go to Types of paint or does it totally depend on the plastic?
It really depends. Take polycarbonate PC.
Okay.
That one's way more sensitive. The wrong paint could damage it.
Wow.
You gotta watch out for chemical compatibility.
So, like picking the right skincare. You wouldn't put a harsh chemical on sensitive skin, Right. All right, so we got our surface and we gotta paint.
Now the fun begins.
Time to unleash our inner artist.
We got it.
Lets talk techniques.
There are a few different techniques.
Okay.
Spraying is great for covering large areas quickly.
Like what kind of stuff?
Like a car part or big toys. Usually the best way to go for those.
And it creates a nice smooth finish, right?
Exactly. But what if you don't have all the fancy spraying equipment?
Yeah.
What about us DIY folks?
You can always brush it on.
Brushing.
Yeah. It gives you a lot more control for those detailed areas.
Okay, so for small objects.
Yeah. Or intricate design.
Right, Right.
It's like having a tiny pen versus a big marker.
Hmm. I've never been good at getting a smooth finish with a brush though.
Ugh. The key is to use thin, even coats and let each coat dry completely before the next.
That's probably where I mess up.
Brushing it and using the right brush.
Does that really matter?
Oh, yeah.
Like what should I be looking for in a brush?
Well, first off, what kind of paint you're using?
Okay.
Some canes work better with natural bristles. Others need synthetic bristles than the size and shape of your object and how detailed you want it to be.
Okay, so a small brush for details. Exactly. Then there's dip coating. Right?
Right. Remember that paint bath we talked about?
Yeah. That seems good for weird shapes.
Yeah. It's great for even coverage on those tricky objects.
Cool. So we prepped picked paint, applied it. Are we done?
Not so fast.
What else is there?
Drying and curing. And it's not as simple as just letting it air dry.
Really? I always thought once it was dry to the touch, you're good.
There's a bit more to it.
Like what?
Drying is just the first stage. That's where the solvents evaporate. But curing, that's where the paint actually hardens, becomes a tough, long lasting finish.
So we can't rush the process.
Not if you want it to last.
Okay. So how do we make sure it dries and cures? Right.
Well, it depends on the paint.
Okay.
Some dry at room temp, like nitrocellulous lacquer.
Okay.
But others, like polyurethane, might need heat.
To help it along.
Yeah.
Like we gotta Bake it at the right temp for the right time.
That's a great way to think about it.
So what if we get that wrong?
You risk the paint not being as durable.
Ah, so it could chip and peel easier.
Yeah. And you don't want all that work to go to waste.
So following the instructions is super important. We've covered prep, paint, application, drying, curing.
Sounds like we've covered it all, but.
There'S still more, right?
Oh, yeah. We got to make sure our work is good.
You mean make sure it looks good and it'll last.
Right. We need to talk about quality inspection.
That sounds important.
It is, and that's what we'll cover next time.
Okay. Well, I think for now, our listeners have got a good start.
They do. They'll be painting prose in no time. Welcome back to the Deep Dive.
All right. We talked about surface prep and picking the right paint. Yep. Now let's get into those application techniques. Okay. We touched on spraying and brushing, but I want to know more about when to use each one.
Choosing the right technique is key for a good finish.
Right.
Spraying is definitely the way to go if you want smooth, even coverage over a large area.
Yeah, I can see that. Like for car parts or something.
Exactly.
But I'm guessing you need special equipment for spraying.
Yeah. Usually a spray gun, air compressor, and a spray booth.
Right. To catch all that overspray.
Yeah. So it's not always the easiest for everyone to do that.
So what about us rigging?
Well, you can always brush it on.
Brushing. Yeah. More DIY friendly.
Definitely.
And you have more control. Right. For smaller things.
Exactly.
For those details, like tiny decorations or something.
Yeah. Or if you have a really intricate design.
I always have trouble getting a smooth finish with a brush, though.
The trick is thin coats and letting each one dry completely before doing the next.
Yeah, that's probably my problem. I rush it and make sure you're.
Using the right brush for the job.
Oh, the brush matters?
Oh, yeah, Big time.
Always just grab whatever's closest.
Well, think about the paint you're using first.
Okay.
Natural bristles are better for some paints, synthetic for others.
Interesting. I never knew that.
And think about what you're painting too.
Right. Like a big brush for big areas. Small brush for details.
Exactly. Now remember dip coating.
Oh, yeah. The paint path.
Yeah. Great for even coverage on those weird shaped things.
Yeah, for sure.
It's often used industrially for painting lots of parts quickly.
Are there other techniques that are more like industrial scale?
Oh, yeah. There's electrostatic spraying.
Electrostatic sounds Fancy.
It uses static electricity to attract the paint to the surface like a magnet. Basically, it's super efficient.
So that's for when you need, like, really precise and durable paint.
Yeah, like in automotive or aerospace.
Cool. So we've got spraying, brushing, dipping, electrostatics.
Yep. Lots of options.
Wow. Who knew there were so many ways to put paint on something?
It all depends on the project.
All right, once we've got that paint on, we gotta talk about drying and curing.
Yes. Very important.
It's not just wait until it feels dry, right?
Nope.
We touched on this before, but there's more to it.
Yeah. Drying is just the first step. The solvents evaporate.
Right.
But then it has to cure.
And that's when it hardens.
Exactly. That's when it forms that tough, durable finish.
So, like, what's actually happening in the paint when it cures?
The molecules are forming chemical bonds with.
Each other, so it all becomes one solid piece.
You got it.
So how do we make sure it cures properly?
The key is following the instructions for your specific paint.
Ah, okay. Because some need heat and some don't.
Exactly.
So what happens if we mess up the curing?
It might not be as durable.
Like, it could chip easier.
Yeah. Or even peel off completely. And nobody wants that, especially after all that prep work.
So we got to get the temp and the time right.
Like baking a cake.
Perfect analogy.
Got to follow the recipe we covered.
Prep, paint, application, drying, curing.
Phew. That's a lot.
But there's one more step.
Oh, yeah.
We gotta make sure all our work paid off.
That's right. Time for quality inspection.
Okay, that's next time.
Can't wait.
We're back talking all things painting, injection molded products. We've come a long way from prepping to painting to drying. Now it's time to see if it was all worth it.
Right. Quality inspection.
This is where we see if our work is truly a masterpiece.
We want it to look good, but it also needs to last.
So what does a quality inspection even look like?
Well, we're looking for any little thing that could be wrong. Both how it looks and how durable it is.
So, like, we're detectives looking for clues.
Exactly.
Okay, let's start with the visual stuff. What are we looking for?
Imagine you're holding it under a bright light.
Okay.
We want to see if the color is even and the gloss is consistent.
So no weird spots that are duller or a different color.
Right. And we're looking for defects.
Like what?
Sagging.
Sagging.
Yeah. Where the Paint dripped or ran.
Ah. So it's not smooth.
Nope. It's uneven.
Yeah, it happens if you put too much on at once.
Yeah. Or if it doesn't dry properly between coats.
Okay. What else?
Orange peel.
Orange peel, like the fruit?
Yeah. The paint looks bumpy. Like an orange.
Oh, yeah, I've seen that.
It's usually from bad spraying technique or the wrong thinner.
Definitely doesn't look good.
Nope.
Any other things we should watch out for?
Blistering, cracking.
Uh oh. What causes those?
Could be the paint isn't sticking right to the surface.
Ah.
Or maybe it was too thick so it didn't cure evenly.
So we gotta be thorough.
Every little detail matters.
Okay, so we've inspected it visually and everything looks good. Now what?
Now we test how well the paint is actually stuck on there.
Adhesion.
Exactly.
How do we do that?
There are a few different tests.
Okay.
One is the scratch test.
So we just try to scratch it off?
Well, not just randomly. We use a special tool.
Oh, so it's controlled.
Yeah. We're seeing how much force it takes to scratch the paint off.
Makes sense.
If it comes off easy, then the adhesion isn't good.
So that tells us how it'll hold up to like, daily use.
Exactly. What about the tape test?
The tape test, what's that?
We stick tape on, then peel it off fast.
Okay.
We're looking for how much paint comes off with the tape.
Ideally none.
Right, Right. If a lot comes off, that means the adhesion is weak.
So maybe we prepped it wrong or use the wrong paint.
Yeah, could be.
So scratch test for toughness, Tape test for how well it's bonded.
Yep. Those two give us a good idea of the overall durability.
Are there other tests we might want to do?
Oh, yeah. It depends on the product and what it'll be used for.
Right. Like if it's going to be outside.
Exactly. We might do a UV resistance test.
To see if it fades in the sun.
Yeah. You don't want the color to wash out.
And if it's going to be around.
Chemicals, we'd do a chemical resistance test.
So we're thinking about the real world use?
Absolutely. It's all about making sure it lasts.
This has been awesome. We covered a lot from start to finish. It's amazing how much goes into painting something. Right. It's a process, but when you know the steps and take your time, you.
Can create amazing work that'll last. Exactly.
So to everyone listening, go out and paint. I got this.
Remember to have fun and try new things. And always remember, the magic's in the details.
That's all for today.
Happy painting,
