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Applying Old Masters

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Forum topic by wpgraham posted 08-04-2021 02:15 PM 305 views 0 times favorited 3 replies Add to Favorites Watch
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wpgraham

1 post in 54 days


08-04-2021 02:15 PM

My wood shop currently uses Old Masters interior water base product for finishing. We used to use foam brushes to apply but even this left streaks. We now use a Kobalt latex paint sprayer with an air compressor to apply. We typically add a little water to thin the product. But, we consistently have irregular patterns of finish and often times the finished product looks “scaly”. The sprayer seems inconsistent in the spray pattern, often times too thick or too thin. This is the second of these types of sprayers we have used. Question, does anyone have any experience of applying this finish or using a sprayer with it?


3 replies so far

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CaptainKlutz

4867 posts in 2713 days


#1 posted 08-04-2021 04:58 PM

Welcome to LumberJocks!

“Scaly”?
That is a new word for describing for how finish looks. LOL

Old Masters (OM) has two different product lines; Retail and professional grade, with many products in each family. Not sure which one you are using? Have only use a couple OM solvent finishes, so I can not help directly.

FWIW – OM is wholly owned by Diamond Vogel in Orange City IA; and both have extensive support system for professional products. OM maintains a direct phone line (712) 737-3436 for professional finishers to resolve issues with their materials. Suggest you call them for help?

IME – Spraying WB products consistently is one of the toughest parts of conversion to environmentally friendly finishes.

The surface tension of water is higher, and they don’t flow out as well as solvent base. They also tend to have heavier polymer base, which requires a larger spray nozzle, and much higher CFM to get good atomization. The difference in equipment needed can be staggering, whether it is proper gun or massive compressor. A regular solvent HVLP gun with 1.4-1.6mm tip might need 8-10cfm. A 2.4mm tip WB HVLP gun can use 20+ cfm to lay down finish properly. These very high CFM rates are reason that turbine spraying units are most commonly recommended for spray WB finishes. There are also differences between gun types for WB. A pressure pot/cup gun will spray WB more consistently than a gravity feed gun, as you have more control on feed rate.

Environment impacts WB more than solvent finishes. In sunny/dry Arizona, I have to add extra slow solvents to retard evaporation (Butyl Cellusolve), as water disappears way too fast and I get orange peel. Solvent bumps up the VOC and makes it less environmentally friendly, but it is only way to make it flow well.

A third issue with WB finishes is stearate coated sand paper. Heavy stearate residue on surfaces is like adding soap to water. This soap changes everything if not perfectly mixed together. This can create water spots or rings on surface. Either need to use a low stearate paper, or include a water/solvent surface wash down to remove the residue. Stearate is not as big of a problem as silicone in automotive world, but still must be aware of possible issue, and have controls for consistent surface prep.

Hope this helps.
Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, Doom, despair, agony on me… - Albert King - Born Under a Bad Sign released 1967

View LesB's profile

LesB

3063 posts in 4661 days


#2 posted 08-04-2021 05:27 PM

Two important questions.
1. How old is the finish you are using. This might include time on the store shelf in some case.

2. At what ambient temperature and humidity are you making the applications.

Old finish can cause problems. I usually won’t use a product after about 18 months because I have had problems with them.

For water based finishes temperatures above around 75 (varies with humidity) cause the finish to dry to quickly for the brush strokes or spray droplets to level out. I try to work at 65 to 70 degrees. Below about 60 they can take so long to dry that it allows dust to settle into the finish.

Hope that helps.

-- Les B, Oregon

View bilyo's profile

bilyo

1398 posts in 2321 days


#3 posted 08-08-2021 05:16 PM

“Latex paint sprayer” suggests to me that the tip orifice is quite large; maybe too large. I have had good success spraying a different brand of water based urethane using a low pressure low volume gun with a 1.5mm tip and gravity feed without any thinning. Others with more experience may know better whether the tip size is an issue.

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