Manipulating Crackle Effects

      An extended exploration of way to tweak formulas and applications so as to modify the look of popular "crackle" coatings. July 3, 2008

Question
I'm looking for the best result creating two different kinds of crackle effects. The first effect is using ML Campbell's Crackle Light for a slight pull without showing undercoat over a wet coat of the following three products: Clawlock, Krystal sealer, and Resistant.

Can/should a retarder be added to extend wet time to get more pull and deeper crevices?
We tried using the 35 sheen Resistant and didn't get too much of a bite with the glaze afterwards. Would going to a 10 sheen increase crackle effect and also allow glaze to bite more? We tried several techniques that worked okay but would like to come up with a better, more dramatic crackle.

Clawlock worked the best, followed by Krystal, with Resistant having the least desired results. We tried medium body glaze, heavy body, vintage and Amazing. None of them had the desired effect because the depth of crackle was not enough. When we went over it to take off excess, not enough was left in fissures to make it pop the way I was looking for.

Effect two: Putting down a crackle before shooting a coat so it pulls and shows the sub layer, either a shader or a pigmented undercoat. We have not tried this yet and want some pointers on techniques/materials to achieve it. I assume there is a different crackle mixture? Would adding retarder to topcoat let it pull more? We are sticking with Krystal sealer, Clawlock and Resistant, so it needs to work with these if at all possible.

Forum Responses
(Finishing Forum)
From contributor C:
From reading their info, the Crackle Light is no more than a thinned out version of their regular crackle, both of which are flatting agent in fast dry solvent. Flatting agent is normally made up of zinc stearates, which are metal soaps. When a normal viscosity full crackle coat is applied to an nc/vinyl finish under it, two things are taking place. To understand this you first have to know the nature of solvent evaporated finishes such as nitro/acrylic/vinyl and others.

First, when a coat of fresh nitro, for example, is applied, it is pretty uniform in thickness if sprayed properly from edge to edge. As the solvent evaporates, the film starts to shrink, pulling away from the outer edges pretty uniformly also. That's one of the reasons it's easier to sand through the edges of the coating compared to the center. When using flatting agent, this still holds true. Whether you're randomly applying it to areas or coating the whole piece beneath the sprayed area(s), you are flash solving the nitro/etc., which is accomplished by the solvents in the flatting agent. Then, within a very short time as the nitro starts to dry again, it begins to re-shrink, pulling the more rigid and faster drying flatted film apart when it does, usually in a random but still consistent pattern. To see this for yourself, all that is necessary is to spray a coat of the crackle and time how long it takes till you see the cracks forming. Then do the same again and as soon as the area is sprayed, immediately blow air on it and you will see it crackle quicker than if sprayed and allowed to start cracking on its own with no outside influences.

This is happening because you are evaporating the solvents present more rapidly than normal. The thicker the flatting agent is put over the nc and the fresher the nc is, the more reaction you will have. The thinner the flatting agent is applied or also thinned out before application, the smaller the cracks will be and of course since the flatted layer is thinner, the depth of the cracks will also be decreased.

I have used full strength flatting agent to produce incredibly large cracks that actually form islands and make the surface look like an otherworld globe would appear. Your final results depend on two things mainly, the stage of dry the nc/acrylic/vinyl is in and the amount and thickness of the crackle medium. For example, if you put 5% retarder in the nitro, etc. and let it dry for just a little while, 30 min or less, and then apply the full normal crackle over it and blow air on it immediately, you will obtain very big crackle. The more or the heavier coat you apply, the bigger and deeper the crack, depending on whether you let it dry by itself or manipulate it with air. The same holds true using the thinner version, which you can make yourself by just thinning out with fast thinner or toluol (see what the main solvent is by checking the MSDS), and then applying lighter coats of this. If it's not as cracked or deep as you desire, then simply bulk it up with more of the regular crackle and if too heavy instead, thin it out more at about a rate of 5% at a time.

Keep proper records of what you've done at every stage and make sure you make good size samples before starting the actual job so that you are absolutely sure of how it is going to turn out in the end. For this I usually use a 4x4 piece of laminate laid up on 1/4" ply. This way if I don't like the look I achieved, I can just wash it off with thinner and start over, thus avoiding using up wood unnecessarily. Also make up or prepare 1 good board for the final acceptable effect you get and a step board showing each process that was used and what it looks like at the stages it goes through from beginning to end. With knowledge of these basic principles, you should, with practice, be able to create any type crackle that can be done with these products. Even the gun setting (fan width, air pressure, oz per min, etc.) will affect the final outcome and repeatability, so be adamant about record keeping - it's the one mistake most people make and wish they had not.



From contributor C:
PS: A couple of companies I worked for in Florida also use a brushing technique to apply the flatting agent clear over a base coat color of Benjamin Moore latex. The latex dries for 4 hours and then the crackle is brushed on with a 2" disposable brush in 4 or 5 inch strokes, each overlapping one another till the whole piece is done. It cracks differently than a spray application in longer cracks but gives a very unique look. The pigment type and amount will also affect the look, so try to keep your pigment addition as low as possible and still get opacity needed.

One other thing if you decide to spray the crackle over the under coating. Keep in mind you will have to do the same throughout the entire project, and any variance from what your original results are will have to be repeated in the exact same manner. Think hard on your testing and scheduling as to what you want to accomplish per day for these affects. This is another area to be well thought out in advance. I've seen many a job go awry because things like this were not taken into account beforehand.



From contributor C:
Oops - on the latex base crackle, I mentioned the latex was sprayed with a good coat 4 mil of acrylic lacquer before the crackle was applied by brush.


From the original questioner:
Not shooting nitro based; this is all post-cat materials.

How do I get the effect to increase? Thinner/retarder in finish? Lower/higher sheen material?

"The thicker the flatting agent is put over the nc and the fresher the nc is, the more reaction you will have."

Again, this is not NC finish but post-cat - not sure if the same applies. We are shooting both at the same time for the over crackle (haven't done the under yet). The sub-coat is laid on in double box coat and the crackle light was spot sprayed randomly over step boards immediately while still ultra wet.

"The thinner the flatting agent is applied or also thinned out before application, the smaller the cracks will be, and of course since the flatted layer is thinner, the depth of the cracks will also be decreased."

Not thinned at all - shot straight up.

"I have used full strength flatting agent to produce incredibly large cracks that actually form islands and make the surface look like an otherworld globe."

Okay, so it sounds like I should use the full strength crackle and thin down as desired?

It sounds like you are saying to let the subcoat do a full flash off. Is this correct? How can the dried surface pull back? I think I am missing something?

"Keep proper records of what you've done at every stage."

We document everything. In fact we were creating master step boards when this happened.

I also noticed you mentioned nothing about sheen levels for the Resistant (which we had the worst results with). We don't do latex.



From contributor C:
According to the product info on the MLC site, this is to be applied over either a vinyl/nitro or other solvent evaporative coating - not over a pre/post cat. If they have told you different, get back to me. Once a post-cat sets up past a certain point, it will not act like I've stated. A pre-cat, yes, maybe - depending on how long you wait. If your supplier told you it could be done over post-cat, then that's a new one on me. I can help you no further if that's the case. All I've stated has to do with evaporative solvent finishes only. The only time I've used over polyester is when I've first sanded and applied a bonding coat of vinyl or other and then the crackle, but that is not what you're using.

This is probably why your results are what they are. All you're getting is the normal action of the flatting agent cracking apart that it does by itself like it would on a sheet of glass or metal or any other non-mobile surface. Dry flatting agent cracking is not going to get you where you need to go.



From contributor I:
I use them over Magnamax, but not CV. With the crackles, we will shoot a coat of Magnamax and wait for it to skin, then shoot the crackle and let it do its job, then when everything cures, we will scuff, glaze if needed, and shoot a final topcoat. I have also found that when you want a colored crackle, you can get a really neat effect by shooting a coat of Magnamax and waiting for it to skin, then shooting a coat of Amazing Glaze over it. As the Max cures, it will pull the coat of AG apart so that the under color is exposed between the cracks. It is a neat effect, but don't ask how I discovered the technique.


From contributor C:
After re-reading all of MLC's material on the three crackles they offer, there is no mention of using these products over any conversion finishes - period! You need to read how it is intended to be used. Yes, you may get cracking by spraying over Magnamax, Krystal, or other conversion finishes you use, but you will not be able to get the many affects that are possible. These products are made to work with evaporative coatings for proper results. In your case you will have to spray the crackles over a normal non-catalyzed vinyl coating only, then apply the crackle, then seal with another coat of non-cat vinyl and then apply your conversion finishes.


From contributor R:
Campbell's Crack-L-Lite is designed to be used over post-cats as well as other finishes.


From contributor C:
My apologies. I did not read about the wet on wet application, only the dry. This is still not the way it should be used if you're looking to manipulate the crackle affect, but if they feel comfortable saying to apply over their cats in that manner, so be it. I still would not waste my time doing that anyway.

I think you'll agree there is very little manipulation that can be done on a wet on wet cat, pre or post, compared to using an evaporative coating, and that this will allow for some of the things trying to be accomplished by the original post.



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