Latex Polyurethene help

[Jim Kirkpatrick]

I hope your between-coat sanding is very light, otherwise, with thin coats sanding can be a futile effort. It never made much sense to me to put a coat on then sand it off. I like to put on 2-3 thicker coats (experience with a particular product helps one to push the sag envelope), then sand only before the final coat. I think Jeff Jewitt recommends a similar process (he's a finishing expert/guru/demi-god/etc). With WB polys, though, I like to use shellac as a sealer first, as it will help reduce the amount of grain-raise from the WB poly.

Yes, very light with a 320 or 400 grit paper....just a light kiss with the paper. Enough to take the nits out. I use a lacquer sanding sealer for the same reason, to minimize grain raising.

[Jim Kirkpatrick]

Is there any reason why you don't want to do just a BLO and shellac finish? And then end up with a wax rubbout? Given the application, you're not talking about wear as you would with furniture so poly or other hard top coat doesn't buy you a lot.

Whats a "BLO and shellac finish"

[Jim Becker]

Whats a "BLO and shellac finish"

Application of BLO (boiled linseed oil)...wipe on, let sit for a half hour, wipe off any excess...followed by shellac a few days later. De-waxed shellac if you intend to top coat with any water borne finish or anything containing polyurethane.

[Jim Kirkpatrick]

I ended up putting this project on the back burner as I was frustrated with finish results in the cold months of winter. I finished the mantel top and top apron assembly in May when temperatures were well above 60 degrees F and had MUCH better results. The poly flowed off my brush and self leveled with minimal foaming. I'll never use latex poly again in the winter if I can help it, I'll use shellac or lacquer. Just a followup picture of the end result which I also designed. I still have to install base boards. Overall I'm pleased with the results.

[Jim Becker]

Just a clarification...it's not "Latex" polyurethane. It's water borne poly....which is an acrylic with some polyurethane resin added. A water borne "poly" isn't the same animal as an oil based polyurethane varnish that is formulated using polyurethane resin, oil (typically BLO) and some other things and then cooked at the factory to make it into a varnish. The urethane resins added to the water borne acrylic don't really enhance it much, frankly. Using a high quality water borne product from a company that isn't mass marketing it will often make a difference in the results. But yes, water bornes do have some temperature requirements that will also affect the end product.

[Howard Acheson]

>> but it is water based. I was under the impression you can thin it with water but not a solvent.

Do not thin a waterborne finish unless the label says you can. If the manufacturer does not state how to thin, don't until you get info from the manufacturer.

As Steve has said, waterborne acrylics only use the water to carry the other chemicals and keep them apart. As the water evaporates, the other chemicals come into contact and sort of melt together into a film. If too much water is present, the other chemicals may not come into contact and the secondary chemical action will not occur.

[Jim Kirkpatrick]

Just a clarification...it's not "Latex" polyurethane. It's water borne poly....which is an acrylic with some polyurethane resin added. A water borne "poly" isn't the same animal as an oil based polyurethane varnish that is formulated using polyurethane resin, oil (typically BLO) and some other things and then cooked at the factory to make it into a varnish. The urethane resins added to the water borne acrylic don't really enhance it much, frankly. Using a high quality water borne product from a company that isn't mass marketing it will often make a difference in the results. But yes, water bornes do have some temperature requirements that will also affect the end product.

Moses smell the roses....whatever.