⚠️READ THIS BEFORE TOPCOATING YOUR GUNPLA⚠️
hej! After finishing my last kit I realized some issues with it and previous kits that could be fixed by topcoating, namely paint scratching off, protecting water slide decals, making the finish look a little nicer, and preventing white parts from yellowing under sunlight (even a little bit of indirect UV light can cause it). So here's my process and experiences:
TOOLS:
-Topcoat spray can: comes in gloss, flat, and matte. I bought gloss and matte only, pictures of the final results will be at the end of the post. In this case I got the Mr Hobby UV cut (i might do a long term update)
-painting clips: you can either buy these or diy them by connecting alligator clips to satay sticks
-paint stand: A quick search on shopee will give options to buy. However after a closer look at these and watching people airbrushing on youtube I realized this is just cardboard with the corrugated parts facting upwards for you to stick the sticks in. Since I had a cardboard box at home, I decided to diy a stand by sticking a bunch of sheets together
-make up brush: brush off any dust from the kits before spraying
-mask: the smell of the topcoat is stronger than spray paint that I have used before. A normal surgical mask and N95 are not exactly designed for filtering out fumes from spray paint, so consider getting a proper respirator which can filter out paint
LOCATION:
I initally wanted to go to an airbrush spray booth. Unfortunately after contacting a few known local places they said they do not offer such facilities for rent, so I had to do it myself. You need a place with open ventilation, but preferably no direct sunlight. For most Singaporeans, this would mean a staircase landing or a multistorey carpark. Lay out some newspapers so you don't make a mess and to avoid complaints from your neighbours.
Singapore's humidity is well above the recommended level to use topcoat at (around 40%). This means you will have a higher risk of trapping moisture under the topcoat layer when you spray, resulting in some splotches on the finish. To reduce this check the weather on the day you plan to topcoat: a hot sunny day, didn't rain recently are good signs of humidity dipping to around 65%, which is the closest to ideal you can get.
PREP WORK
I had some touch ups that I needed to do on some of my kits that I had been procrastinating (painting details, sanding, cleaning panel lines). Now was the last chance to do it, since after that all the details would be locked in. If you're doing this, please do your due diligence to check the parts before topcoating because I trapped some imperfections that I cannot fix (unless I use thinner to removed the topcoat).
I also needed to use masking tape to cover up transparent parts as there is a risk of them frosting up when sprayed, especially with matte topcoat. I masked up holes and ball joints so that the pieces could smoothly fit back together (Bandai Kits are known to have very precise fits in connecting parts, even a coat of paint can cause them to not fit anymore.)
After dismantling the kit to ensure pieces don't cover one another, I gave them a quick dusting to remove any dust.
THE ACTUAL PROCESS
Normally people spray a thin 'mist coat', wait 24 hours, then spray a 'wet coat'. Considering the less than ideal humidity in Singapore and after consulting online, I decided to go with the first mist coat only. After spraying, I left them to sit at the staircase for a few hours, occasionally checking to ensure no one stole it. After that, I brought them in to reassemble. It is recommended to not touch the parts for at least 24 hours for the coat to cure, as there will be risk of smudging. I didn't really encounter this, probably because my coats were too thin.
FINAL PRODUCT
Matte: the plastic surface loses that slight shine that most out of box plastics have. Colour is also noticably duller, especially for darker colours. Plastic feels rougher to the touch, with an almost dusty feeling.
Gloss: Plastic surface looks the same at first, but upon closer look they reflect light slightly better than before. Plastic feels smoother to the touch. Unfortunately I could not get any good photos which will show an obvious difference.
MISTAKES
For some kits, I was not careful and sprayed too much, causing frosting.
Another major issue that I did not expect was the topcoat causing the panel lines to smudge, especially for gloss. Shortly after spraying, I started to notice shallow panel lines and/or those lined using a pour type marker to smudge very badly. Further research online found that gundam marker ink can dissolve in topcoat, likely explaining what happened. I managed to clean some of the smudging off with a gundam eraser marker, but that affected the coating
When it comes to topcoating Gunpla, one important factor often overlooked is humidity. High humidity can trap moisture under the topcoat, leading to unsightly splotches on your model's finish. I found that in Singapore's typically humid climate, it's best to check for a hot, dry day with low humidity before spraying. This approach really helped improve the final look of my kits. Additionally, I've learned that using the right mask is crucial. Ordinary surgical or N95 masks don't filter out spray paint fumes well, so investing in a proper respirator makes the process safer and more pleasant. Another tip is to carefully mask transparent parts and tight-fitting joints before topcoating. My attempts without masking led to frosted clear parts and joints that no longer fit as snugly due to paint buildup. Masking these areas preserves the integrity and appearance of your kit. Regarding finishes, matte topcoat dulls colors and creates a slightly rough texture, which I personally appreciate for the natural look it gives. Gloss coats enhance color vibrancy and smoothness but can cause panel line smudging, especially if you've used Gundam marker inks. To combat this, I recommend testing panel lining techniques and waiting adequate time for ink to dry before applying gloss topcoat. Lastly, assemble your kit with the spray location in mind: place parts individually on a DIY cardboard paint stand with ample ventilation but avoid direct sunlight to minimize risks. I found stairwells or parking garages ideal indoor/outdoor spots for this. Following these insights really elevated the quality of my Gunpla builds and helped protect them from long-term yellowing and physical wear.
This is really helpful! I have a can of topcoat but never knew where to start, thanks for the advice!