Jump to content
ARC Discussion Forums
  • advertisement_alt
  • advertisement_alt
  • advertisement_alt
Sign in to follow this  
Rocky

Primer adhesion

Recommended Posts

I was fixing up an old Monogram P-38J model I had built in 1992, and I needed to put a white stripe around the nose. The plane was recently painted with Model Master enamel aluminium colored paint, and it was thoroughly dry. I had a new bottle of acrylic-polyurathane Vallejo Surface Primer that I wanted to try out, and it was white, so I figured it would be just dandy for the job. It wasn't. When I pealed off the masking tape, the primer came up with it. I thought primer was the stuff that was supposed to stick to surfaces better than paint!?

100_6808_zpszhr0weuj.jpg

Share this post


Link to post
Share on other sites

Hi Rocky,

I can't really say why this has happened but, it would be better to have a clean surface instead of a painted one, when applying a primer. Primers are probably not designed to stick to any surface but, only on clean-ones.

Share this post


Link to post
Share on other sites

Did any of the underlying paint come up?

I agree that the surface of the model does not look clean, and any acrylic paint want's a clean surface.

I assume the metallic paint is new. You say it is thoroughly dry, but you may be deceived. Metallic enamel paints outgas and cure more slowly than other enamels, due to the nature of metallic pigments, which actually impede the migration of solvents out of the paint.

Share this post


Link to post
Share on other sites

That being said, Vallejo's primers seem to be notorious for adhesion problems. There have been a number of complaints. (google is you want to see more instances)

Share this post


Link to post
Share on other sites

That being said, Vallejo's primers seem to be notorious for adhesion problems. There have been a number of complaints. (google is you want to see more instances)

From a chemical point of view, that's not too surprising. I can envision an acrylic-urethane polymer, but it's likely a new, not entirely understood or completely tamed beast.dry.gif

Ain't technology wunnerful!

Share this post


Link to post
Share on other sites

I only use Vallejo primers if I have like a week of drying time to spare, or it just won't be sandable nor will it stick very well. It's cheap and easy to spray with good coverage though, so I use it now and again... actually more as a color sometimes, than a primer. I prefer Mr Surfacer and Mr Finisher for pretty much everything. Did the primer peel, or the paint below the primer?

Share this post


Link to post
Share on other sites

Not especially surprising -Vallejo tube putty doesn't stick to anything either. TBH, I'm having some difficulty understanding how these products became so twendy! :dontknow:

Share this post


Link to post
Share on other sites

I never had trouble with their primer coming up. but it needs to go on clean plastic, and it IS NOT sandable.

The paints are popular because they blend very well and are easy as pie to brush.

Share this post


Link to post
Share on other sites

As stated by others, primer needs to go on a clean, normally unpainted surface. I have never used any Vallejo products, but I believe that they are mostly acrylic products. I use primers that are solvent based, because they bite into polystyrene plastic. This makes a better bond. I like lacquer-based primers because they dry much quicker than enamel. You just have to work it right because it not only likes to bite the plastic, it likes to eat it as well! Lacquer products can also be re-constituted if some of the solvent evaporates.

Added: Oops! Sorry, but a word about safety. Always wear a (normally dual cartridge) organic vapor respirator. Remember, if you can smell it, it's getting inside you. This includes acrylics. A lot of folks, including me, build in the basement. If your house has a basement, that's where the furnace usually resides, as does mine. I use a paint booth with a squirrel cage fan. I vent the fumes out through a basement window. I vent the fumes out through 4" dryer hose.(the flexible stuff with plastic covering) I make sure that the end of the hose is at least 6 feet from the house so the fumes don't find their way back inside. Keep a fire extinguisher within reach when painting.

Edited by balls47

Share this post


Link to post
Share on other sites

Try Badger's Stynylrez and you'll think differently about non-solvent primers. It's simply the best I've found that doesn't try to kill me at the end of a spraying session. I love solvent-based primers but I just can't spray that stuff in the house. Vallejo is definitely crap in a bottle. I never got along with their primers or their Model Air range. The Model Color range is, however, superb. Best brushable paints I've found.

Rob

Share this post


Link to post
Share on other sites

Did any of the underlying paint come up?

I agree that the surface of the model does not look clean, and any acrylic paint want's a clean surface.

I assume the metallic paint is new. You say it is thoroughly dry, but you may be deceived. Metallic enamel paints outgas and cure more slowly than other enamels, due to the nature of metallic pigments, which actually impede the migration of solvents out of the paint.

None of the aluminium paint came up. Parts of the model were a little dusty, but not where the primer went on. That surface had been repainted. It had days to dry.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...