Preparing Sprayable Filler

Introduction:

This trick is an oldie but a goody and one I’ve not used in a while due, in large part, to my goal of using fewer lacquer-based reagents. Since I’ve cleaned my act up and use about 90% acrylic paints these days, I’ve brought this technique back to my bench.  It’s lacquer-based so requires proper ventilation (paint booth) and a personal respirator but it’s a trick that can save a lot of time while simultaneously ensuring that unfilled seams and other surface imperfections are caught prior to spraying paint.

The real utility of this technique is the ability to control where filler is sprayed versus using a spray can of Mr. Surfacer which often results in coating the entire model, especially if it’s 1/48 or smaller. When properly diluted, the average airbrush should be able to deliver atomized filler as a 2-3mm wide line permitting just seams and joins to be sprayed. As with any paint, a light coat of filler will reveal any seams that need filling or other imperfections that will ruin the final finish.

Most importantly, small imperfections such as a partially filled seam can be filled in by repeated passes with the airbrush. This is really handy. A small seam on the leading edge of a wing can be airbrushed away as opposed to filling, sanding, and blending by hand. Once the filler is dry, a quick blending with Micromesh 6 or 8,000 (wet) results in a mirror-smooth finish that’s ready for primer.

Preparing Sprayable Filler:

I suspect that, like me, many of you have a bottle or two (or 5) of liquid filler such as Mr. Surfacer 500 (or similar) sitting around in the bottom of your workbench drawer. I’m sure you know that after Mr. Surfacer sits undisturbed for a while the heavier component (filler) settles to the bottom of the bottle.

The goal is to collect as much of the settled filler or putty as possible while getting as little of the overlying solvent/carrier. Once collected, the putty will be re-suspended in Gunze Leveling Thinner for spraying. In my hands, the concentrated putty, re-suspended in Leveling Thinner, sprays better with less clogging and less dry over-spray than does a straight dilution of shaken Mr. Surfacer.   

 

 

I collect the settled filler with a stainless steel spatula or similar. Mixing of the settled filler as you do this is inevitable but try to get as much dry filler and as little of the liquid as possible. Oh yea, this may be a little messy 🙂

After a couple swipes of the spatula, approximately 2ml of settled filler is placed in a graduated paint vial or similar container.

To this, 3.0ml of Gunze Leveling Thinner is added to the vial along with a stainless steel mixing ball. The filler is then suspended in the thinner by vigorous shaking.

 

 

 

 

 

 

Once prepared, sprayable filler can be stored in a leak-proof container indefinitely, ready to spray when you need it.

A few uses for sprayable filler are illustrated below using the Eduard 1/72 Hellcat as our victim, er subject. This is an awesome kit that pretty much drops together providing the modeler with a quick, easy, and detailed build. Well done, Mr. Eduard.

I’m building my Hellcat as a night fighter and therefore had to fill multiple square holes in the bottom of the wing intended as mounting points for stores not carried on this version. After the holes were filled with stock styrene and blended with a little filler I opted to check the work with a coat of sprayable primer. 

 

Spraying the Filler:

For spraying I use my trusty H-S Infinity fitted with a 0.2mm tip at ~18psi. That’s higher than the 12-15psi I use for spraying most paints but is required to get atomization of the filler.  And, yes, you read that right—a 0.20mm tip.  Many guys think that spraying filler requires a larger tip (0.40mm or bigger). This is not always correct. Mr. Surfacer Filler, diluted appropriately in Gunze Leveling Thinner, sprays perfectly fine through a 0.20mm tip–no problem. If the filler mix is too thick it can be easily adjusted by adding a few drops of Leveling Thinner directly to the paint cup.

Adjusting the dilution of filler to get a relatively fine line (2-3mm) allows for better control over where the filler is applied permitting finer details to be avoided. This is especially true when multiple passes over an unfilled seem are required. 

The Mombo Combo Paint Vial Set:

5ml Vials x10

10ml Vials x10

Stainless Steel Mixing Balls x20

Paint Vial Storage Rack

 

 

Another seam-filled area that required checking was the belly. Multiple small seams, left unfilled on panels toward the rear of the fuselage, were filled completely with a couple of passes of the airbrush. Additional seams in the belly area were too deep to be filled with sprayable filler and were filled the old fashioned way: Filler, Sandpaper, and Micromesh.  

 

 

 

 

 

The eye is naturally drawn to the cockpit of most model aircraft. That being the case, seams in and around the cockpit area will be scrutinized to a higher degree than those on the belly. I quick swipe with the airbrush revealed the seam directly in front of the windscreen was sufficiently filled and ready for primer.

Conclusion:

Sprayable Filler: easy to prepare, easy to shoot, and one sure way to detect and fill small seams and imperfections that will ruin that final finish you’re aiming for. I hope you found that helpful. If you have any questions drop me a line at john@modelpaintsol.com.

 

Now go paint something!

–John 

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