To Wash Or Not To Wash Before Applying Finish To A Decalled Model

[ai5629]

I did a search before deciding to post this, but did not see it addressed previously.  For those that paint and decal their models, what do you do between completing decal application and applying your finish coat(s) to your models?  For almost 40 years, I have always washed my models between the aforementioned steps with dish liquid and water.  I must have read about it or been told by more experienced modelers when I was starting my first projects back in the mid 80's.  (I have always believed this step removed oils, dirt and most of the lint on the models.)  I have to reapply decal solution to the washed cars before the finish coat(s), due to the decals getting some of the soap solution under them.  This usually gets resolved with a few applications of MicroSol.  I washed ten completed cars tonight, and some of the decals washed off and needed reapplied.  I am wondering if the washing step is really necessary.  Or perhaps, someone has an alternative that works just was well.  Thank you in advance for your comments.

Jeff

[nickelplate759]

I wash, but gently.   Not nearly as rigorous as before painting.

Mild detergent solution, brush gently with a soft sable paintbrush, rinse.  Final rinse with distilled water, because my water is quite hard.

Gently.

[nkalanaga]

I just rinse mine off with tap water and, usually, a cotton swab.  Enough to get any glue residue off, but I don't scrub them.

[robert3985]

I also wash my models in warm tap water with a drop or two of Dawn dishwashing liquid mixed in.  I also brush with a soft sable watercolor brush (a quality brush), then, wearing new Nitrile gloves, I remove the model from the soapy water and rinse with distilled water (my water is also hard).

I take my model down to my spray booth and with the air pressure at around 35 to 40 psi and holding my airbrush about a foot away, I blow the water away...inside and outside..., then, after it looks like the water is gone, I blow it off again just to make sure.  This gets the oil-based surface contaminants off of the model.

To get any wax-based contaminants off...and more persistent oil-based contaminants, I gently brush on new (clean) Bestine (Heptane) to the surfaces that I'll be decaling.  Bestine evaporates very quickly, so you only need to wait a few minutes until you start to decal.

When I decal, I would like to wear fine Nitrile gloves, but that doesn't work for me, so I wash my hands and fingers thoroughly before starting to decal to minimize any skin oils that may have accumulated.

After the decals are done and thoroughly dry and I've inspected them to make sure the decals are free of imperfections and bubbles, I give the model another light brushing with Bestine before applying a sealing coat with my airbrush...handling the model again wearing new Nitrile gloves.

This procedure works very well for me and I haven't had a oil/grease/wax contaminant decal failure since I became competent building and painting plastic models in my early teens 65 years ago.

Cheerio!
Bob Gilmore

[peteski]

When I apply decals and decal setting solutions it usually results in visible spots on the model's surface.  Not a hard water spots but likely remains of the setting water/setting-solution mixed with traces of decal's adhesive (the water soluble stuff - usually dextrose - that makes decals slide off the paper) which dries on the model's surface. I use a very soft brush and warm water with some dish-washing solution (like Dawn) to gently dissolve those spots. I do it very gently -  the spots will dissolve away quickly.  The bush I use is usually a 1" very soft sable artist brush but a clean makeup (never used for makeup) brush will also work

Then I put the model under gentle stream of warm water to rinse it clean.  Next, hold the model in one  hand and I tap it  on my other hand to shake of most of the water.

For final drying I have either blotted the remaining droplets with a clean lint-free towel, or use compressed air (but at pressures lower than Bob).  After that I put the model in a dehydrator for few hours (at around 110 deg. F) to make sure all the moisture is gone before the final clear coat.

I have never experienced soap collecting under the decal's clear film or have decals peel off the model.

[robert3985]

...After that I put the model in a dehydrator for few hours (at around 110 deg. F) to make sure all the moisture is gone before the final clear coat.

I have never experienced soap collecting under the decal's clear film or have decals peel off the model.

I've been threatening to get a dehydrator for years.  Maybe I'll do it this year!?  I understand they're also very good for quickly curing paint so I won't have to wait 24 hours between coats of enamel-based paints.

Cheerio!
Bob Gilmore

[peteski]

I've been threatening to get a dehydrator for years.  Maybe I'll do it this year!?  I understand they're also very good for quickly curing paint so I won't have to wait 24 hours between coats of enamel-based paints.

Cheerio!
Bob Gilmore

That is correct Bob.  Many automobile modelers use them to accelerate paint drying on plastic automobile bodies.

[Westcoast_Trains]

I wash my to be painted parts with 70% before I paint, and I paint only with Vallejo water base. Tried Tru Color and other brands of paint but they stink so much and are difficult to work with in my opinion. I always apply a coat of clear matte after painting before decaling. I also use the nitrile gloves during the entire process so no oils etc. I think that most of that is pretty much considered standard practice

[Jesse6669]

A word of caution to modelers with 3D printed models:  Cured resin will react to water, and so my advice would be to avoid washing them, especially un-painted models. 

Most 3D resins react to moisture until primed/painted, and even to some degree afterwards, with the effect being warping, curling, or cracking of thin and delicate parts.   

Decal solvent can also do it;  I had a logo plate on one of my 3D printed Z scale autoracks--a very tiny part about 2x3mm and only 0.10 mm thick-- primed and painted, and I applied a logo to it, hit it rather liberally with MicroSet and it curled.  I switched to 0.2mm styrene for these parts.

[bbussey]

A word of caution to modelers with 3D printed models:  Cured resin will react to water, and so my advice would be to avoid washing them, especially un-painted models. 

Most 3D resins react to moisture until primed/painted, and even to some degree afterwards, with the effect being warping, curling, or cracking of thin and delicate parts.   

Decal solvent can also do it;  I had a logo plate on one of my 3D printed Z scale autoracks--a very tiny part about 2x3mm and only 0.10 mm thick-- primed and painted, and I applied a logo to it, hit it rather liberally with MicroSet and it curled.  I switched to 0.2mm styrene for these parts.

Hmmm ... I've never had that problem, as long as I let newly-printed models dry post-cleaning for at least 24 hours before UV curing.

[peteski]

Aren't there different 3D resins out there? I would suspect that a water-cleanup type of resin might be affected by water after curing.

[robert3985]

Although I haven't had any fresh prints react to water, I don't wash them before painting since I have just taken them out of a thorough alcohol bath.

If I had handled them a lot before painting and decaling, I'd most likely just use Bestine (Heptane) to remove waxes and oils.

I haven't had any paint/decal adhesion problems on any of the finished models that have had to be assembled before being painted.

Here's one of the latest project...I did the prints from Anthony Kochevar stl's, and my partner Jared is doing the assembly, painting and decaling...

Photo (1) - MOW Equipment:


These are still under construction with additional paint and decals yet to be affixed.  Proper flatcars are also in the making...

Cheerio!
Bob Gilmore