CaptainSoup Posted October 27, 2018 Share Posted October 27, 2018 It's getting colder outside so it's time to start using my airbrush to prime my models. I've been using Vallejo Surface Primers to achieve this but I've noticed something interesting. After the primer dries on the model, if I scratch the primer with my fingernail it comes off easily, and I mean with no effort or force at all. Regardless of if I spray from the pot or use a thinning agent in the airbrush. This isn't the case with my spray can primers (GW, Army Painter, etc.) Where I can go rough on the layer of primer and their isn't a scratch to be seen. So my question is why the Vallejo primers are so scratch susceptible in comparison to spray can primers. Thanks for reading! Link to comment Share on other sites More sharing options...
Spears Posted October 27, 2018 Share Posted October 27, 2018 Personally I found the same thing, anything I primed with vallejo airbrush primer just rubbed off when handling or in foam. I have switched back to rattle cans for primer. Link to comment Share on other sites More sharing options...
Kokoshi Posted October 27, 2018 Share Posted October 27, 2018 GW cans propellant kind of "melts" the plastic and the paint : the result is absolutely "unscrappable". Don't know for other brands, but I guess it is more or less the same. Link to comment Share on other sites More sharing options...
zedatkinszed Posted October 27, 2018 Share Posted October 27, 2018 The GW cans are acetone based. They "cure" as they as they dry and are ready to base paint in under an hour (even though I would not recommend moving that fast TBH). The Vallejo primers are PU (polyurethane) based and take 12 hours to cure fully. Acetone is a naturally occurring solvent and PU is a synethetic polymer. They have completely different chemical reactions and compositions. Really they are not comparable products - by that I mean, despite the fact that they do the same thing they do it in completely different ways. You need to let the PU primer act like a PU primer and not expect it to behave like a solvent based one. To be honest I've never had a problem with either rattle can or airbrush primer flaking or scraping off plastic models. Metal minis is a different story though. Link to comment Share on other sites More sharing options...
Lior'Lec Posted October 27, 2018 Share Posted October 27, 2018 I’ve used the Vallejo polyurethane primer on a couple of models recently as well but didn’t have those problems. In my case I brushed it on one evening then came back to actually paint it a few days later (I tend to have long days at work so frequently can have a week or more between paint sessions). Like @zedatkinszed pointed out maybe it needed more time to cure, but when reading online I saw that Vellajo does not recommend thinning it, even if using an airbrush, so in the case of the thinned primer this could also be a factor. Link to comment Share on other sites More sharing options...
CaptainSoup Posted October 27, 2018 Author Share Posted October 27, 2018 Thanks for the replies guys. I think Zed really nailed it on the head. Since the spray primer melds into the plastic it makes it much tougher to scratch. Valljeo is still a great product line, just gotta make you avoid things that can scratch the primer before the paint is on them. Link to comment Share on other sites More sharing options...
RuneBrush Posted October 31, 2018 Share Posted October 31, 2018 The paint within a GW can is known as an "etching" paint, so acts in a similar manner to plastic glue melting the surface slightly before curing. Vallejo surface primer acts more as a "binder" to ensure that your paint grips properly. It's one of the reasons that if you strip a model back that's been undercoated with a GW spray can, the plastic will look dirty I've found that you're actually OK spraying in the cold weather - but you have to be a bit more aware of the weather conditions, a slight breeze or dampness in the air will give you a poor finish. I also keep all of my spray cans indoors at room temperature as that'll mess things up too! Link to comment Share on other sites More sharing options...
syph0n Posted October 31, 2018 Share Posted October 31, 2018 1 hour ago, RuneBrush said: The paint within a GW can is known as an "etching" paint, so acts in a similar manner to plastic glue melting the surface slightly before curing. Vallejo surface primer acts more as a "binder" to ensure that your paint grips properly. It's one of the reasons that if you strip a model back that's been undercoated with a GW spray can, the plastic will look dirty I've found that you're actually OK spraying in the cold weather - but you have to be a bit more aware of the weather conditions, a slight breeze or dampness in the air will give you a poor finish. I also keep all of my spray cans indoors at room temperature as that'll mess things up too! I used to undercoat all the time in the garage as a kid. It was just as cold as outside! Like you say, keep the cans warm. You can even run warm water over the cans. I find well shook cans make most difference. Link to comment Share on other sites More sharing options...
CaptainSoup Posted October 31, 2018 Author Share Posted October 31, 2018 Thanks for the additional info guys. For my current project I need to use white primer. I have GWs but we're all aware of how bad of a finish it can give which is why I hesitate. Is it really viable to using running water on the can? I hear people use a port of boiling water but I dont have any pots big enough lol. Link to comment Share on other sites More sharing options...
zedatkinszed Posted November 1, 2018 Share Posted November 1, 2018 19 hours ago, CaptainSoup said: Thanks for the additional info guys. For my current project I need to use white primer. I have GWs but we're all aware of how bad of a finish it can give which is why I hesitate. Is it really viable to using running water on the can? I hear people use a port of boiling water but I dont have any pots big enough lol. Don't use boiling water! Warm (not hot) water in a bucket for 10 minutes is fine. Stay away from extreme heat with pressurized cans! Link to comment Share on other sites More sharing options...
RuneBrush Posted November 1, 2018 Share Posted November 1, 2018 The general rule of thumb I use is that if after I've shaken my can a couple of minutes, my hand feels quite cold, the can needs warming up Know what you mean with the white primer - one thing I have found fairly reliable is to undercoat using GW's grey primer and then airbrushing the miniature white (Vallejo). Though it's more work, it gives a much more reliable finish. Link to comment Share on other sites More sharing options...
zedatkinszed Posted November 1, 2018 Share Posted November 1, 2018 2 minutes ago, RuneBrush said: The general rule of thumb I use is that if after I've shaken my can a couple of minutes, my hand feels quite cold, the can needs warming up Know what you mean with the white primer - one thing I have found fairly reliable is to undercoat using GW's grey primer and then airbrushing the miniature white (Vallejo). Though it's more work, it gives a much more reliable finish. This! On both counts. The other thing I do is prime with Chaos Black and then Zenithal highlight with Corax White or with airbrush and then a slight white drybrush. Link to comment Share on other sites More sharing options...
CaptainSoup Posted November 1, 2018 Author Share Posted November 1, 2018 1 hour ago, zedatkinszed said: Don't use boiling water! Warm (not hot) water in a bucket for 10 minutes is fine. Stay away from extreme heat with pressurized cans! Right of course. I'm not sure why I said boiling lol. Back to my question though, could I not just run how water over the can for a few minutes rather than going through the trouble heating up water in a bucket? Link to comment Share on other sites More sharing options...
stato Posted November 1, 2018 Share Posted November 1, 2018 11 minutes ago, CaptainSoup said: Right of course. I'm not sure why I said boiling lol. Back to my question though, could I not just run how water over the can for a few minutes rather than going through the trouble heating up water in a bucket? Yeah no problem, just dry it off after to make sure it doesn’t rust or anything. As with previous comments just warm water, if it hurts your hand it’s too warm. Sprays work best at room temp, so you just need to get them to that, sticking it under your jumper for 10min would probabaly do the same thing. Link to comment Share on other sites More sharing options...
zedatkinszed Posted November 1, 2018 Share Posted November 1, 2018 43 minutes ago, CaptainSoup said: could I not just run how water over the can for a few minutes rather than going through the trouble heating up water in a bucket? Warm water from the hot tap (again like @stato said, just lukewarm water rather than hot water) is fine. It doesn't need to be a big deal - just fill a jug with warm water and pour it into the bucket. Equally the can might fit in the sink The can needs a few minutes in the water so if you pay for water then this is far cheaper than leaving a hot tap running. Other people just leave the can in a warm room overnight which is a much simpler solution TBH. Link to comment Share on other sites More sharing options...
CaptainSoup Posted November 1, 2018 Author Share Posted November 1, 2018 29 minutes ago, zedatkinszed said: Warm water from the hot tap (again like @stato said, just lukewarm water rather than hot water) is fine. It doesn't need to be a big deal - just fill a jug with warm water and pour it into the bucket. Equally the can might fit in the sink The can needs a few minutes in the water so if you pay for water then this is far cheaper than leaving a hot tap running. Other people just leave the can in a warm room overnight which is a much simpler solution TBH. Got it. Thanks for the information! Link to comment Share on other sites More sharing options...
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