Is water-based polyurethane and polyurethane sanding sealer both suitable?

I found the water-based polyurethane made by Behr. They also have a water-based polyurethane sanding sealer. The ingredients seem to be the same, but it costs less than the regular finishes. Is this suitable? If it's the same stuff, only thinner to penetrate better then it might end up heavier, right?

From : Don Stackhouse

If the viscosity of the sanding sealer is actually lower, then it would tend to penetrate deeper, which could increase the weight. More care on your part and applying lighter coats could compensate. I'm not personally familiar with that particular product, but most of the sanding sealers I'm familiar with contain fillers (such as talc) to plug up the holes in the wood. Most of those fillers are heavier than the base resin in the paint, so I would expect them to add weight. Because of the fillers, they also tend to be HIGHER viscosity than the equivalent paint. Of course, if the plugging and sealing action of the fillers prevents the paint from soaking as far into the wood, it's still possible it might not weigh too much. Once again, very light coats with adequate drying time in between is the key. Still, if the sealer you're considering uses talc (which is basically ground-up rocks!) I'd be nervous about using it on an airplane!

Don Stackhouse @ DJ Aerotech
djarotec@bright.net
http://www.bright.net/~djwerks/