How To Panel Line Model Kits
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The Tamiya panel line accent color bottle says it will make your kit "pop" with "a single application." That's marketing. The truth is it will also make your kit look like a crime scene if you don't know what you're doing.
I've been panel-lining kits for 25 years, and I've ruined two kits learning the hard way. I've also judged two local Gunpla competitions where the difference between a winner and an also-ran was almost always the panel lining.
Here's how to do it without crying.
The Tools I Actually Use
You don't need a lot of gear. You need a proper panel liner (like Tamiya Panel Line Accent) — not a basic paint set. I've been using the same bottle for three years and it's still half full.
You need a bottle of lighter fluid, a cotton swab, and a pair of metal tweezers. The plastic tweezers included in kits are useless.
I've said it before and I'll say it again: if the designer never tried to use the tweezers, they shouldn't include them.
The Vallejo Basic Colors set is a paint set, not a panel liner; use Tamiya Panel Line Accent instead. It's thin, it flows well, and it doesn't dry out in the pot. The AK Interactive 3rd Gen Thinner is a paint thinner, not a panel liner. Use it only for thinning paints, not for panel lining.
The Technique That Works
The secret to panel lining is that you're not painting. You're letting capillary action do the work. You touch the tip of the applicator to the engraved line and the ink flows along it. That's it. The problem is when you touch the tip to a line that's not engraved, or when you apply too much pressure and the ink floods the surface.
My technique after two decades: I dip the applicator in the bottle, touch it to the end of a line, and let the ink flow. I don't drag it. I wait a few seconds, then I take a cotton swab dipped in lighter fluid and wipe along the line to remove the excess. The lighter fluid evaporates quickly, so I have to work fast.
The HG Gundam Aerial was the first kit I built after a 15-year gap. I panel-lined it with the Tamiya accent color and it took me about 20 minutes. The result was night and day. Without the panel lining, the kit looks flat. With it, the kit looks like it came out of a showroom in Japan.
The Mistakes You Will Make
You will flood a panel line. You will get ink on a visible surface. You will try to wipe it off with a dry cotton swab and smear it. I've done all of these. The fix is to use lighter fluid, not water. Water won't touch the Tamiya accent color. Lighter fluid dissolves it instantly.
The second mistake is using too much pressure. The Tamiya accent color is thin. If you press the applicator hard against the plastic, the ink floods out and pools. You'll spend more time cleaning up than you spent applying.
I learned this on the MGEX Strike Freedom. The gold plating is beautiful, but it's also fragile. I panel-lined the inner frame before I realized it would be completely covered by the armor.
That was 12 hours I'll never get back.
The third mistake is panel-lining before you've cleaned the nubs. If you have a nub mark on a surface, the panel lining ink will pool around it and make it more visible. Sand the nubs first. I use a glass file for this, and I've been using the same one for two years.
The Tamiya Panel Line Accent Color
The Tamiya Panel Line Accent Color is the best product for this job. It flows well, it dries in about 10 minutes, and it's forgiving if you make a mistake. The downside is the smell. It's strong. I work in a converted spare bedroom that smells like plastic cement and regret, so I'm used to it. But if you're working in a small apartment, open a window.
The bottle has a small applicator tip that's perfect for getting into tight spaces. The RG 1/144 Zaku II (Shin Matsunaga Custom) has a lot of small panel lines, and the tip got into all of them without any trouble.
I've also used the AK Interactive 3rd Gen for panel lining. It's a good product, but it's thicker than the Tamiya, so it doesn't flow as well. I have to thin it with a bit of thinner before I use it, which is an extra step I don't need. The Citadel Base Paints are good for hand-painting details, but they're not my first choice for panel lining.
How to Fix Your Mistakes
You will make mistakes. The fix is simple: lighter fluid and a cotton swab. Dip the swab in the fluid, wipe the excess ink, and the plastic is clean. The Tamiya accent color is enamel-based, so it doesn't bond to the plastic instantly. You have a window of about 30 minutes to clean up before it's permanent.
If you're working with a gloss-coated kit, the cleanup is even easier. The ink sits on top of the gloss coat instead of soaking into the plastic. I top-coat my kits with a gloss clear before panel lining. It's an extra step, but it makes cleanup much easier.
The HGUC Zaku II (Shin Matsunaga Custom) was a nightmare to panel line without a gloss coat. The plastic is a dark green, and the ink soaked in almost immediately. I had to be very careful. With a gloss coat, it would have been a 15-minute job instead of an hour.
The Bottom Line
Panel lining is the single biggest upgrade you can do for a kit. It costs ~$10 for the bottle and takes about 20 minutes per kit. The result is a build that looks like it came out of a showroom in Japan.
The Tamiya Panel Line Accent Color is the product I recommend. It flows well, it's forgiving, and it lasts for years. The AK Interactive 3rd Gen is a good alternative if you want to support a smaller brand, but it needs thinning and it's not as easy to use.
I've been building kits for 25 years, and I've tried every panel lining product on the market. The Tamiya is the one I keep coming back to. It's not the cheapest, but it's the best.
And whatever you do, don't panel line the inner frame of the MGEX Strike Freedom. You'll spend 12 hours on it and then cover it all up with armor. I learned that the hard way.