Vallejo chipping medium eats everything!

[Cromm Cruac]

I'm trying to master the chipping technique using the chipping medium. I know it could be done with hairspray but I've chosen Vallejo Chipping Medium.

I've had initial problems with spraying this as it comes from the bottle - its gelatine consistence just makes an airbrush clog and spurt big droplets. However, I've managed to overcame them with diluting using some Ultimate Thinner. It sprays more nicely with thin coat.

I've followed these steps - with 24h to cure between steps - except 4-5 where I've waited about 6h and 5-6 maybe an hour:

1. prime with Ultimate Primer

2. spraying base coat of Vallejo Model Air

3. sealing with coat of Klear

4. spraying Vallejo Chipping Medium layer

5. applying top layer of Vallejo Model Air

6. Applying some water and started scrubbing and chipping

 

All goes well but then despite having a protective coat or Klear, the chipping medium start to eat through base layer down to a primer. I can see that even if I just scrub gently the base coat is being dissolved, colouring the top coat.

 

What am I doing wrong? Could it be Klear coat that reacts with chipping medium making it stronger? Should this protective coat be any particular type, maybe not water based, maybe it should be like enamel or lacquer - what should it be? Should I wait 24h to cure all layers including top layer?

Please help!

 

 

[Ade H]

Bearing in mind that your process is quite far away from mine (which I can describe later on if you want me to), it's tricky to know whether I have a fair picture in my mind of what you're doing/not doing, and I have not got around to testing the Vallejo chipping medium, it is difficult for me to do much more than hazard guesses and throw random thoughts at you...

 

When I try something new, it will always involve some testing, for which my starting point is usually a video (ideally, from the product's manufacturer); then I widen my test from there if I need to, trying to be as organised as possible as I go (e.g. changing one thing at a time).

I'm curious why you feel the need to do step 3: I don't know if you're actually making problems for yourself, probably not, but you're certainly not saving any there. You're using so many coats of one thing and another... Also, could you give the ref number from the bottle? I think that both chipping products are exactly the same, just different sizes... but your description of how thick it is doesn't seem to tally with mine (bearing in mind that I've not sprayed it yet, as I'm happy with my current process and just bought it a while back to test).

Talking of process, one specific oddity which does leap out at me is your very short time to chip. OK, I'm using HS, so it may not be directly comparable, but I've learned to wait way longer than an hour!

And how are you spraying the MA in step 5? Again, different people and processes here, but when I'm chipping, I use my thinner/water premix instead of pure thinner. It's a pity that I can't really know how your spraying technique compares to mine, just in case there's anything to be changed there.

Edited January 23, 2022 by Ade H

[Cromm Cruac]

I've seen some tutorials on YT and also read some. That's why I use a coat of Klear because I've read that having some 'sealing' layer helps with the issue I have. Some recommend gloss layer, some matt but I couldn't find if this need to be the same type of paint or other - like using enamels for weathering if paint is water based acrylic.

To answer some your questions @Ade H, the chipping medium I use is 73.214. I spray MA paint in about 50/50 ratio of paint to Ultimate Thinner. I find that applying more light coats of diluted paint works better for me.

I do the chipping with water only as this what Vallejo (and tutorials) recommend.

I'm gonna prepare another test and will wait at least 24h after each coat. Also with different seal layers (and without).

[Ade H]

You shouldn't need a clear coat under HS or chipping fluid. There can be edge cases when a particular hairspray is too rich in alcohols for certain paints, but that is only likely to affect the uncured top layer during removal and should be much less likely to affect a properly cured base layer. But as with all processes, we test first before committing so that edge cases can be discovered; doing things on the slight chance of having some undefined and unevidenced problem is one step up on the hoodoo scale from making a sacrificial offering to the gods of modelling... 😄

 

By the way, don't put a gloss layer under a chipping layer unless you really want it to fly off... It needs tooth to work properly. That's why chipping over metals can be tricky. I had intended to mention that earlier but I was thinking of a lot of things at once. By "Klear" you mean that floor polish which some modellers use? There's a distinct lack of tooth right there...

 

214 is the 17ml bottle, IIIRC. Like I said, it should be 100% the same, They are listed together in the catalogue and there's nothing in the text to distinguish between them. The official video shows only the 35ml, for what that's worth. Although airbrush pressures are somewhat personal choice, was yours just too low for it? There are some auxiliary products which you would think would never belong in an airbrush, yet somehow they can be sprayed (nozzle and pressure permitting).

 

About that thinner. I've never used it and it may be absolutely brilliant (despite being marketed as suitable for umpteen different paint chemistries...) but I definitely prefer to stick with proprietary thinner and water when doing chipping because this is a complex process with a lot of chemistry (and a dash of pure alchemy) involved. I've put in a fair bit of time to get a system which works consistently for me and there really is no substitute for that.

Edited January 24, 2022 by Ade H

[Cromm Cruac]

So finally got some time to do the chipping tests. I'm posting the results in case someone has similar problem.

 

 

All the layers were sprayed in at least 24h intervals to allow curing. After all has been cured I've wetted the areas and started chipping.

 

1. Klear protective coat: chipping was easy and quite detailed but after a while of soft scrubbing the Klear layer gave up and chipping medium started to eat the gray undercoat showing the primer.

2. No protective coat: chipping medium went through the gray undercoat layer immediately in wider areas

3. Matt acrylic varnish coat: top layer was immediately dissolved and chipping was very crude and flaky. Then it went through the undercoat layer.

4. Lacquer protective layer: best results, very detailed and I had to scratch hard to damage the undercoat gray paint. Soft scrubbing didn't damage the gray layer.