Custom-Formulating Spray-Only Stains

      A wide-open discussion on how to formulate and mix spray-applied stains, using the whole range of ingredients available in the market. February 19, 2006

Question
We are typically using dyes in a washcoat, wiping oil stains and dyes in our toner coat to get our color. For some jobs I want to start using pigment as well as dye or even instead of the dye to reduce the color shifting. We are willing to mix our own stains with raw pigment or use something already made. Does anyone have any recommendations on which products to use?

Forum Responses
(Finishing Forum)
From contributor M:
We are using a spray only stain from ML Campbell. The Campbell rep mixes our stain for us. It is made with SB2 Spray only stain base. We generally mix this 1:5, again with SB2. I have been pleased. This concentrate included both dyes and pigment.



From contributor D:
I like the SB2 a lot given its limitations. It only accepts 6 ounces of colorant - pigment or dye or a combination of both per gallon unless I want to risk adhesion issues, which I don't want to do. That's roughly 5% - 6% color strength by volume. Weight is not a useful measurement especially since some colors weigh more than others.

Often, I need a spray only stain that has much stronger color strength than what 6% gives me. I make my own pigmented spray only stain using Huls 824's. I mix no more than 3 ounces of color into 40 ounces of lacquer thinner. That gives me 7.5% color strength. For pigmented spraying that is plenty. Akzo-Nobel gave me a basic formula for making a spray only stain liquid vehicle for use with Huls 824's.



From contributor D:
Here is a spray only stain base that I use. I have to plead a little bit of ignorance on this because the first ingredient is one that I never heard of and my Google search turns up nothing to help me.

Lactose spirits: 40 ounces
Naptha: 75 ounces
Mineral spirits: 13 ounces
824 or 844 Huls: 20 ounces or less
Another stain base suggested to me is:
Mineral spirits: 24 ounces
Lacquer thinner: 8 ounces
824 or 844 Huls: 4 ounces or less



From contributor R:
The 844 colorants contain no binder, so to use them in a solvent only stain system could lead to future adhesion problems. If you really must make your own, rather than use the store bought kind, then use lacquer thinner to reduce some vinyl sealer down to about 3% solids and add no more than 5 ounces per gallon of the 844's. If your formula calls for gilsonite substitute a brown/walnut dye instead. 5 ounces per gallon is the maximum pigment load that a low solid stain base like this can safely handle.


From contributor C:
Being that many paste colorants today are being made without a binder, this feature allows these colorants to be used in many types of coatings and coloring mediums. The ethylene glycol that is used in some of these paste colorants allows you to mix these colorants into both solvent and water base mediums. You can add a little of your coatings, as it will act as the binder if needed.


From contributor G:
I have made a lot of spray stains using (as bases) ethanol w/resin, VM&P/w resin, lacquer thinner w/lacquer added at 5% for resin and straight xylene. As colorants, I've used NGRs, microlith, dyes, Microton, Artis and 844s.

One formula called for a 5 gal pail of 844 TW added to 40 gal xylene with no resin, which brings me to my points: First, 844 colorants, especially the high SG ones - TW, RO, YO - will settle out of any spray stain base. There are not enough resins to hold them in suspension. You need a pot agitator.

Second, even at that tint percentage (way higher if you calculate weight ratio since TW weighs about 80 lb/5 gal) there were never any adhesion problems. This was on a high production automated finishing line. If there were problems, they'd have been reported. Finally, when calculating the pigment load of a spray stain, only pigments (pastes) are counted. Dyes and Microtons are freebies.



From contributor R:
The guidelines that we have from Campbell for mixing 844 pigments in a 2 1/2% spray only stain base are 5% by weight, Microtons 5% by weight and dye concentrates 5% by weight. For the 10% wiping stain base it is 25% for the 844's, 5% for the Microtons and 10% for the dye concentrates - all by weight. We blend several hundred gallons of custom stains per week using these guidelines.

As Contributor G said the volumetric weight varies by color with RO the highest at 58.23 grams per fluid ounce to PB at 29.08 grams per ounce. Settling of the heavier pigments and floating of the lighter pigments can both be a problem so keep that in mind.

In my experience mixing stain formulas are like prunes. Sometimes you are not sure if 6 ounces is enough or if 3 ounces is too many. A formula that may have worked a hundred times before all of a sudden goes south on you because of some minute variation in weight, temperature or who knows what.

Find a company that you are comfortable with and whose products you like and use it. Follow their guidelines and specifications and eliminate some of the anxiety in your life. Most manufacturers offer several types of bases and are willing to share the info necessary for you to use them successfully. Most also offer custom formulations. Face it, their R&D departments and long term testing are more advanced than anything most of us can come up with. I'm not saying to give up on experimenting, just do it when you have time to test and sample properly, not when you are under the gun to get a job done.

One final thing to remember is that he who makes the topcoat rules. If you have a failure and you are not using the topcoat manufacturers stains/bases or are outside of their guidelines then all bets are off.



From the original questioner:
About Contributor G's observation that Microtons and dyes are freebies - does this mean that the load capacity of a stain base is calculated only with respect to pigments and that dyes and Microtons could be added without care, or is there an upper limit to adding these items? I haven't taken the time to find out exactly what Microtons are but perhaps an answer to the question of how much dye/Microton is too much could include some explanation of why and not just the manufacturers' recommendations.


From contributor J:
I find Sherwin-Williams to have the most variety of colors. Theirs stain bases are very universal and are easy to reproduce consistently. Their products all seem to work together well. Their dye stain concentrates will reduce with any liquid (water, alcohol and almost any solvent.)


From contributor G:
To the original questioner: Dyes are formulated such that the coloring agents are completely dissolved in the vehicle. Microtons are similar in that the colorants in the Microtons are extremely fine, but still particulate. For most purposes, dyes and Microtons are used the same way.

For instance, both can be used as spray stain as is, no additions needed. In fact, they are usually reduced. One of the many reducers that can be used is spray stain base. What difference is there if Microton is reduced by 50% with spray stain base, or spray stain base has a 50% Microton load? If you put them in a wipe stain at too high a ratio, they will interfere with the wipe time and it will dry too fast.

As Contributor R pointed out, the topcoat manufacturers rule. If you want to go outside the posted limits, and you have an adhesion problem, you'll get short shrift if you mix different manufacturers’ products.

If you stay within one brand of products and show due diligence - samples, crosshatch tests, etc, you'll likely be covered by your lacquer distributor, if you ever have a failure. Their posted limits are, of course, intended to limit their liability in the event of a coatings failure. Not surprising they'd want to limit the variables; considering I've seen finishers mix lacquer adding the catalyst by eye.



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