Oil paint varnish help

[modeller_masa]

 

I have a question about oil paint varnish. This is my first time using oil paint. I applied paint layers like this.

I used Winsor & Newton Liquin medium to accelerate the drying of oil paint. 

 The entire model went horribly wrong once I applied the lacquer spray. 😱 It didn't happen when I tested the oil paint and lacquer spray.

 

 

How can I fix the cracked surface? which oil varnish should I use in this case?

[Bob Cleek]

It's difficult to tell from the photo exactly what's happened to the finish, but from what I can see and you've described, it appears that the spray lacquer employed a very "hot" solvent which reacted with the oil paint, "skinning over" (drying quickly on the surface with greatest exposure to the air) and when the lower level of the lacquer dried, it "shrunk" and created the "crackle" finish on the drier top of the lacquer coat. Such problems are almost always the result of incompatible coatings with different drying or adhesion characteristics. 

 

It may also be a function of the incompatibility of the acrylic basecoat and the oil paint over it. Some reaction between the "hot" lacquer solvent and the oil paint causing the oil paint to soften may have resulted in the oil paint being pulled away from the acrylic base coat as the oil paint dissolved by the lacquer solvent shrunk when the solvent evaporated.

 

The different result you had when you tested the coatings on the "coating paper" may have been due to the paper's porosity or surface flexibility permitting the lacquer solvent to evaporate without creating tension between the lacquer and the lower coating layers.

 

Another possibility, and this is a wild guess, is that the drier you used on the oil paint reacted with the lacquer solvent, causing the lacquer to dry more quickly than it should have which caused the crackling in the lacquer.

 

This is all speculation, of course. It would take a chemist to evaluate the compatibility of the various coatings used. Generally speaking, "water and oil don't mix," and water-based acrylic paints and oil-based paints and lacquers shouldn't be considered compatible in any event.

 

You may be able to remove a fair amount of the lacquer and oil paint using lacquer thinner to soften it and wipe it off. Similarly, you may be able to remove the acrylic coating with alcohol or some proprietary acrylic stripper. In any event, a gentle scraping and careful sanding down to bare wood is in order. From there, it depends upon the finish you desire. High gloss finishes are usually avoided on models as the high gloss destroys the impression of reality and makes a model "look like a toy," as some have described it. If you wish to darken the wood, as you apparently tried to do, the proper coating schedule would be to apply an oil based wood stain to the bare wood. Thereafter, the wood could be coated with an oil based varnish and after that had dried well, hand rub the varnish with pumice and rottenstone until the desired level of low gloss was achieved. Alternately, a "wipe on" polyurethane finish containing stain might also be used, but only after testing this on the same wood species with which you used to plank the hull.

 

I'm sorry to see the problem you've encountered. Unfortunately, there's a certain degree of alchemy involved when dissimilar coatings are used, particularly when modern synthetic coatings are used. You just never know what you are going to get. Myself, I entirely avoid using "rattle can" spray coatings and water-based coatings on models because I've had similar difficulties to what you've experienced when I've done otherwise. Fortunately, the damage can be undone with a bit of work.

 

 

Edited February 26, 2023 by Bob Cleek

[Jaager]

I thought that they rules were:

water based acrylics are not compatible with organic solvent based oils.

 

You may have to get back to bare wood.  Trying to make sense of "Coating paper"  - is this a paper model?

 

Anyway - remove the acrylic paint.

Prime with shellac  -

then use oils (enamels)

 

Old school lacquer is in a noxious and aggressive organic solvent.  Very volatile - such that another coat can be applied after 2 hrs.  My initial hypothesis is that the solvent in the lacquer allowed the acrylic layer to interact with the enamel layer.

Why not over coat with shellac instead of an organic solvent based polymerizing oil like linseed  (with a catalyst) = (oil varnish).  You do not need a hard shell for this application.

 

There may be some situations where good money would be spent to get that sort of crinkled finish.  It looks a couple hundred years old.

 

[modeller_masa]

Thank you so much, Bob! I gave up trying to repair the cracked surface and began sanding the entire surface with 800 grit sanding paper. 😂

One of your answers is very promising, so I'll remove all the oil-surface with lacquer thinner. It is definitely easier than sanding work!

[modeller_masa]

@Jaager Yes. It is a cardboard model from Shipyard.

I didn't mention shellac before acrylic primer. I always use as much shellac as possible on all of the parts.   The color of the acrylic primer was tan or flesh, and the color of the oil paint was brown. I needed two colors that contrasted each other to draw the wood grain pattern. The previous painting works were ok except for this entire hull. If I have to remove the acrylic primer, I need another tan-colored paint that doesn't interfere with oil paint or enamel.

Previously, I had no problems with the lacquer spray for industrial. I used a lacquer coat to protect the oil paint surface from further assembly processes. My last works were fine, and the parts were smaller. I didn't try using shellac as a oil paint-varnish because the lacquer spray worked very well. I'm baking some oil painted test beds to try a new set of varnishes, and I'll add the shellac to the list!

[druxey]

As mentioned above, the drying rates are a factor in that craquelure finish. It is unlikely that the acrylic primer was incompatible with oil paint: artists use acrylic primer all the time on canvas and then apply oil over this. The problem lies in either the use of Liquin and rapid drying or reaction between oil and lacquer. If using lacquer thinner, make sure you have good ventilation, no open flame anywhere close by and, if possible, a NIOSH respirator mask. Acetone is nasty stuff.

 

As advised, a gloss finish is not the best choice for a model. I'd suggest acrylic primer and oils paint, but allow the paint to dry slowly using only turpentine with a little linseed oil added as solvent. It's too bad that you had this problem as your paint job looked very well done.

[modeller_masa]

@druxey Yes. I respect the water-oil paint rule, but I sometimes feel that I can use a water based paint at the first-primer layer.

 

 The Shipyard cardboard kit combines elements of both wooden and plastic model kits. Painting is essential to completing this kit, like a plastic sailing ship model kit.

According to general painting guide for plastic kits, I used a clear gloss lacquer spray as a middle coatings between painting layers, which gives a protective surface and prevents blending each layers. The final coat of varnish will be a clear matte lacquer spray. The matte varnish tends to include stone dust, so it doesn't help in the middle of painting work. Uneven surfaces result in the additional painting layer with irregular staining.

Of course, I'll apply another matte varnish because the lacquer spray made this accident... I can't tolerate it if this thing happens again at the very end of assembly. 😱

Edited February 26, 2023 by modeller_masa

[Jaager]

9 hours ago, modeller_masa said:

If I have to remove the acrylic primer, I need another tan-colored paint that doesn't interfere with oil paint or enamel

Should be easy to do.  Just find a tube of artists oils with the shade of pigment that you need.  It may need mixing of two or more.  I just checked Blick's page - Most of their Gamblin 30ml tubes are $9.00.

One of those tubes may last you a lifetime.  Turpentine or mineral spirits for a thinner have a lower cost per volume.

 

I use a lot of brushing lacquer. Certainly not on a model, but to put a thick clear protective layer on my frame patterns - water proof, no smear, thick to stand up to rigorous sanding - it is more Mylar like than just paper, it does not do one thing that I wanted - add a degree of brittleness that a fan of fuzz is not at the abraded edge - still needs frequent Gem blade scraping to see the line.

ANYWAY - lacquer:  too thick, too much shine/gloss for anything but a toy.  The solvent - even the "Green" substitute is a mixture of potential really toxic organic solvents - they make acetone seem like breathing nitrogen for the irritation.   I never would, but if I had to spray lacquer, it would be in a glove box -outside.  The solvent mixture reads like something to use in Death Row - never mind turning whatever lacquer itself into something with a particle size small enough to get into my alveoli.  Even if it is not carcinogenic - layer of it there would impede gas exchange.

[wefalck]

In general, avoid mixing too many media, such as acrylics, oil-paints and organic solvent-based varnishes.

 

And respect the 'fat over lean'-rule

 

Using oils over acrylic paint/primer is not a problem. However, you should give the acrylic time to cross-link and diffuse out the water, which takes several days, if not weeks, depending on the thickness of the layer.

 

The 'drying' of oil-paints in reality is an oxidation process of the lineseed-oil. This takes time. One can speed up the process by adding 'dryers', which add as catalysts. Some pigments act actually as catalysts, which is why some colours 'dry' faster than others. By using solvents, such as turpentine, you reduce the amount of binder, i.e. linesee-oil, in the paint, which is the reason, why oil 'washes' dry faster.

 

As long as this 'drying' process has not been completed, which also can take weeks, one should not apply any varnish. After all, the artists of old held the 'vernissage' of their paintings sometimes a year or so after completion. In any case, I would go for one of the classical varnishes for oil-paintings, rather than for other solvent-based varnishes.

 

As long as you stay within the same paint-system 'intermediate' varnishes in general are not a problem, but the same precaution re. 'drying' times apply, when using such 'intermediate' varnishes.

 

[Bob Cleek]

10 hours ago, Jaager said:

Why not over coat with shellac instead of an organic solvent based polymerizing oil like linseed  (with a catalyst) = (oil varnish).  You do not need a hard shell for this application.

I think he wants to stain the wood and then put a high gloss lacquer over it. Not something I'd advise, but any stain would have to be applied before any shellac. No?

[Jaager]

I used "over coat" trying to describe a last layer.  I think we agree that shellac works well as the last layer?

 

To be too pedantic about it - a stain is actually a semi transparent paint -  so it could go over shellac?  It is pigment particles suspended in a solvent with a binder?

 

A dye is a whole nuther thing.  A dye is single pigment molecules dissolved in a solvent.  No binder, the intent is for the molecules to soak into the wood and change the color.  The grain is unaffected.  The surface is still bare wood.  Using shellac before a dye would be a bad thing to do. It would already be where the dye molecules would go if the shellac was not already blocking them?

 

The careless use of word "stain" to mean changing the color can cause problems for a tyro - which we all were at some point - (and for most things - still are -) but everyone should not have to be a scout -cutting their own new trail and learning the hard way?

 

[Bob Cleek]

6 hours ago, modeller_masa said:

The Shipyard cardboard kit combines elements of both wooden and plastic model kits. Painting is essential to completing this kit, like a plastic sailing ship model kit.

Ah! My bad! I thought that was a wooden hull, not a card model. Take that as evidence of your great skill in creating a faux finish with oil paints!  Forget what I said about using stain. You've done a great job once and after you sand off the lacquer, you should be okay if you just reapply the oil paint faux wood finish (with a bit of drier added.) You can then wait for it to dry well (a few weeks should be enough since the coating will be thin) and then apply two or three coats of shellac and, when dry, hand-rub it to a nice perfectly smooth satin finish. At least, that's what I'd do. As before, be sure to do a test run first, but the shellac should be completely compatible with the oil paint and the alcohol shellac solvent shouldn't have any effect on the oil-based paint.

 

 

[Bob Cleek]

1 hour ago, Jaager said:

I used "over coat" trying to describe a last layer.  I think we agree that shellac works well as the last layer?

 

To be too pedantic about it - a stain is actually a semi transparent paint -  so it could go over shellac?  It is pigment particles suspended in a solvent with a binder?

 

A dye is a whole nuther thing.  A dye is single pigment molecules dissolved in a solvent.  No binder, the intent is for the molecules to soak into the wood and change the color.  The grain is unaffected.  The surface is still bare wood.  Using shellac before a dye would be a bad thing to do. It would already be where the dye molecules would go if the shellac was not already blocking them?

 

The careless use of word "stain" to mean changing the color can cause problems for a tyro - which we all were at some point - (and for most things - still are -) but everyone should not have to be a scout -cutting their own new trail and learning the hard way?

 

Yes, we do agree that shellac works well as the last layer of the coating system. 

 

I mentioned stain because I thought he was working on real wood and not card. My mistake. Stain could go over shellac, but it wouldn't look the same as stain on bare wood. This is because the grain structure of the bare wood absorbs the stain at differing rates and enhances the figuring of the wood. Shellac can do this to a certain extent (especally a darker shellac,) but if the shellac is put down first, it soaks into the wood and any stain will only uniformly darken the workpiece. I agree using shellac before a dye would be a bad thing for the reasons you stated.

 

My use of the work "stain" wasn't careless, it was just wrong, since I thought it was wood to which he was applying the finish instead of cardstock.

 

The ship modeling world would be a better place if we could just convince our colleagues to only use shellac and artists' oils and avoid all the "better living through chemistry" that seems so fashionable these days. Not likely we'll live long enough to see that happen though.  

[Jaager]

59 minutes ago, Bob Cleek said:

My use of the work "stain" wasn't careless,

You got hit by the outer edge of that canister shot.  I was aiming at the general sort of inquiry we get -

 

1 hour ago, Bob Cleek said:

The ship modeling world would be a better place if we could just convince our colleagues to only use shellac and artists' oils and avoid all the "better living through chemistry" that seems so fashionable these days. Not likely we'll live long enough to see that happen though.

We in absolute agreement on this.    

 

[modeller_masa]

Thanks to Bob Cleek's idea, I began antifouling work. A mineral spirit, which is the best for enamel, didn't work, so I'm using lacquer thinner, which is stronger. The lacuquer thinner also removes acrylic paint base, but the coated paper hulls bear it well, fortunately.

 

Also, thank you for your concern for health. I have a fan-ventilation paint booth and am wearing a big gas mask. It is the best way to protect myself in the given situation.

 

I found appropriate oil varnishes. The second picture shows exactly same surface that happened to the hull. I bought a new cheap lacquer spray from a different company, and I guess a different ingredient caused the issue.

The first picture is a Golden MSA lacquer spray, which is the most expensive one. It works just as well as my old, cheap lacquer spray can from different company. 

The third picture is a Zinsser dewaxed shellac liquid. It also made a durable surface with no issues.

 

This is only 12 hour short term test. I'll be watching how they're changed.

 

 

It is a bit off topic. I applied shellac to any wood parts before I applied an oil based gel stain. I believed that the wood conditioner would make surface more flat, so I could paint it more uniformly. In my opinion, the method of applying shellac is determined by the purpose of the painting. I want to remove the grain pattern on a wooden model, so I use shellac as a wood conditioner. If someone wants to show explicit grain patterns of raw wood, shellac isn't good choice. Making furniture is most likely the case in my thought.

[Bob Cleek]

8 hours ago, modeller_masa said:

If someone wants to show explicit grain patterns of raw wood, shellac isn't good choice.

At scale model viewing distances, wood grain isn't going to be apparent. 

 

I'd suggest you also try putting a coat of shellac over your oil paint wood color, let it dry well, and then hand-rub it for a very smooth surface. The tests will be the best proof, but I think that the alcohol solvent in shellac will have no effect on the oil paint beneath it, while the mineral spirits in even a traditional varnish may soften the oil paint beneath it unless the oil paint if well-cured.

[modeller_masa]

Yeah, the third one in the picture is very smooth and dried well. The Golden MSA spray is easy but expensive. In addition, shellac is very good with lacquer spray. I'll apply matte transparent lacquer spray over the shellac layer at the very end of the building. I won't forget to test it before I apply the last spray.  
 

In addition, I've read some strict scoring standards regarding scale model contest. When judges of model contests grade scores, they also check the wood grain pattern because it sometimes makes an inappropriate scale effect. For example, large and complex wood grain patterns of the cherry wood POF model are a penalty. It is a reason senior modellers are looking for non-grain woods such as boxwood and pearwood. It might be too quick to be picky about my materials, but several inexpensive plywood based wooden model kits I've built frequently showed odd grain patterns that didn't look well. "The builder's model" scheme is my favorite. 😎

[wefalck]

Not sure that shellac over oil is such a good idea. Keep in mind that it takes days to months for the lineseed-oil to fully polymerise, depending on how fat or lean you applied the oil-paint. Until then volume changes of the oil-paints can/will occur. Shellac per se is brittle and a pure shellac varnish may crack. That is, as pointed out above, varnishing is normally done months after applying oil-paints and these varnishes are normally mixtures of different resins that show a behaviour more similar to that of polymerised oil-paints.

 

Apart from the fact that indeed one can simulate wood grain quite nicely with oil-paints, I wonder why mix paint systems and use oil-paints at all? I think the wood planking can be simulated well with acrylic paints and then one can use acrylic varnishes to achieve the desired surface sheen.

 

If it was me, I would either use all acrylics or oil-paint and a varnish from a reputable artists' supply house. Three different paint systems over each other calls for trouble, keep it simple. 

[modeller_masa]

11 minutes ago, wefalck said:

the wood planking can be simulated well with acrylic paints

I've researched several wood grain techniques on Youtube and practiced them, and I've concluded that the oil paint-interdental brush is the easiest and cheapest one for everyone. None of the acrylic paint techniques were as simple as the oil paint technique. Even though I tried acrylic paint retarder to simulate the characteristic of oil paint, such as high viscosity and long drying time, I felt it is too delicate for every people like pasting water slide decals. 

 

I was making a tutorial video of the oil paint technique before I encountered this issue. 🤕

 

Yes. The worst feature of oil paint is that it takes months to dry. Too long drying time isn't good for scale model work, especially the plastic model kits.

 

https://www.winsornewton.com/row/masterclass/exploring-liquin-mediums/

My solution is Winson & Newton Liquin, which speeds drying. It cuts drying time down to 8 hours - 3 days, which is incredible. 

 

 

Ok. I finished antifouling the hull. Thank to eveyone for providing such a valid solution and a wealth of interesting knowledge. I'll post the video of the super easy oil paint technique with an additional varnish guide.  

 

[Bob Cleek]

10 hours ago, modeller_masa said:

Yes. The worst feature of oil paint is that it takes months to dry. Too long drying time isn't good for scale model work, especially the plastic model kits.

 

https://www.winsornewton.com/row/masterclass/exploring-liquin-mediums/

My solution is Winson & Newton Liquin, which speeds drying. It cuts drying time down to 8 hours - 3 days, which is incredible. 

As you probably know, artists' oil paints are formulated to provide the maximum drying time in order to provide the artist with a paint they can work with, moving it around on the canvas for as long as it might take them to complete a painting. Artists oils generally use raw linseed oil (also called "flax seed oil" under which name it can be found in any health food store.) ("Boiled" linseed oil is raw linseed oil to which driers have already been added to speed up the drying process.) The proprietary driers you are using, such as Liquin, do speed up drying time, but nowhere near as much as would be desired for regular painting rather than artists' oil paints. You want the more powerful stuff, generally sold in hardware and paint stores as "Japan drier." Follow the mixing instructions on the Japan drier container. Think of your artists' oils as "concentrated paint, just pigment and linseed oil, which should be considerably thinned with turpentine, mineral spirits, or acetone, (depending on the user's preference... like a barbecue sauce recipe) and Japan drier to speed the polymerization of the linseed oil base. By adding the correct amount of Japan drier, one can accelerate the drying time of an oil paint as much as is desired. It appears from the manufacturer's literature that Liquin is only intended to modify the artists' oil paints within in the much narrower spectrum of drying times required for classic artists' oil painting techniques, rather than for fast drying times appropriate for modeling.

[modeller_masa]

Thank you, Bob. I've never heard about the "Japan drier". The Japan drier is a dilute version of cobalt lineate, and the Liquin is alkyd. There is one more drier, "LEAD naphthanate".

https://products.richesonart.com/products/copal

http://langridgecolours.com/cobalt-driers/

 

When I tested the wood grain technique, I found that viscosity is an important factor to keep a clean grain pattern. I've tested several Liquin series, from fine detail to impasto, which have different viscosities, and concluded that the Liquin light gel is the best application for this case. The Japan drier seems to be a more legitimate speed drier for oil paint, but I may need additional gel medium to maintain high viscosity.

Edited February 27, 2023 by modeller_masa

[Jaager]

4 minutes ago, modeller_masa said:

When I tested the wood grain technique, I found that viscosity is an important factor to keep a clean grain pattern. I've tested several Liquin series, from fine detail to impasto, which have different viscosities, and concluded that the Liquin light gel is the best application for this case.

I followed up on your introduction of Liquin.  The Liquin fine detail has one characteristic that is counter to what a model ship wants.  It is a gloss product.  The original Liquin is low gloss - which is not great - but better.  The increased viscosity in the light version is produced by the clear carrier solution.  When it evaporates, most of what produces the increased viscosity is gone?  By using tubed artists oils, the concentration of pigment is under your control.  An increased pigment concentration would have an increased viscosity that remains after polymerization.  But now that I think on it:  impasto is not a good approximation of an adzed planking surface.

[modeller_masa]

1 hour ago, Jaager said:

impasto

One of my goal is cheap and easy technique for newcomers. I'm using cheap and disposable brushes, such as Q-tips and an interdental brush. As we know, solvent based paints are hard to clean, and the thinners are very toxic. Newcomers, including me, may want a "brush and forget" disposable brush.  

Due to the limited painting tool, the Liquin impasto didn't work well with my interdental brush. The light gel made exactly the same viscosity of oil paint after mixing, and the other Liquin, Original and Fine detail, made tube oil paint wet, which blurs grain patterns. My explanation will be more clear when I post video guide. 

 

By the way, I don't care about the gloss finish in the middle of painting work. It can be turn into matte finish anytime with matte transparent lacquer spray. It is important to keep a glossy and clean surface between painting layers. According to Winson & Newton's description, Liquin isn't and can't be a varnish. An additional varnish coat is mandatory, and I prefer to use lacquer spray. UM... except for this case.

Edited February 28, 2023 by modeller_masa