It depends on 3 things.
What you are painting.
Whether you are applying latex, oil-base, or primer.
What size TIP you are using.
We use spray equipment and use size 17 and 19 for latex, and 11 for oil.
Double-check the size that came with your gun and look at tips at Home Depot.
Old tips wallow out and the spray pattern is irregular/uneven and the gun blows out too much paint and our material costs go up.
The manual says "dilute correspondingly" http://www.airless.com.au/Airless%20Sprayer.pdf
Let's say you are spraying oil-base stain: I would NOT dillute this material.
Oil-base primer: 1 thinner to 4 paint
Latex primer: use a roller and brush so you have a good undercoat for the paint.
Oil-base paint: I would add 1/8 thinner with 1 paint, and be careful of runs
Latex stain: try 1 water to 4 stain
Cheap interior flat latex: 1 water to 4 paint
Latex semi-gloss interior: 1-1/8 to 4 paint and apply very thin coats and let dry between coats.
Cheap exterior flat latex: 1+ to 4 paint, and add more or less water as needed
Good exterior latex paint: use a roller and brush because the purpose of latex exterior pain is to apply heavy protective coat over outdoor materials ... dilluted exterior latex will not give sun and mildew protection.
We use heavy spray equipment and apply exterior latex straight form the can. It's the only way to give lasting job, unless you're doing a temporary playhouse.
The key to successful spraying is to strain your paint to get out the lump and clogs - BEFORE putting paint into the gun.
We always strain the paint unless it's a freshly opened can.
If can was opened yesterday, we strain it.
That because paint gets a dry film that will clog the sprayer.
First you need to mix your material, so you need a couple buckets.
Pour the paint and thinning material in 1 bucket, and then to mix, pour back and forth between two or three buckets. This action will mix the paint thoroughly and save you an hour of rotating a paint stir stick.
Next, you need to strain the paint.
Wash out a 5-gallon bucket.
Buy 5 gallon strainer that fits into bucket.
Pour material into bucket with strainer, lift strainer up and then grab end of strainer and squeeze out all the paint.
Immediately put lid over paint so no drying film will form.
Wash out strainer.
You're ready to put paint in spray gun.
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