High humdity: water or oil based top coat?

[Robert Engel]

I'm getting ready to finish a dining table top and can't afford to have a mishap.

Seeing that finishing is my weakest point, and reading some recent posts about finishes clouding, I'm concerned about this due to the high humidity here. I'm concerned about prolonged drying time.

My plan was to spray an oil based polyurethane top coat (Arm R Seal Satin). Of course, this was supposed to happen 2 months ago, but ....

Should I be looking at a water based product? What alternative finishes do you use & recommend?

The top is 42x84 QSWO that will be dyed with a water based dye then a couple coats of shellac sealer. I'm trying to avoid brushing or wiping type finishes. Or should I?

Thanks, guys. I'll be posting some pics of the project soon. I think I've come up with a neat alternative to trestle base construction.

[Jim Becker]

Well....I personally wouldn't "spray" an oil based product, but that's me. The dry time is so slow that any overspray makes a big mess. I personally use water borne products which are easy to spray and can be had in very durable versions these days, so that's what I'd use. While I'm a Target Coatings user and probably would choose something like EM8000cv or EM2000 for this, General Finishes has some nice products that other forum users like a lot. The EM800cv is a very durable conversion varnish type product. The EM2000 is a water borne alkyd emulsion that has more of an oil-based "color" to it.

[John TenEyck]

I agree with Jim; no way I'd spray Arm-R-Seal. The overspray will make everything it hits a fly strip and it will take forever to dry on your table. I would use a WB topcoat. Lots of good choices from GF, TC's, and others. For simple I'd look at EM-2000, as Jim suggested, or GF's EnduroVar, or Sayerlack from SW's (sorry, can't remember which one at the moment).

John

[Wayne Lomman]

I agree with Jim and John. Don't spray oil based product!

Humidity is a problem no matter what coating you are using. As a general rule, you will be OK if your relative humidity is less than 85%, your air and substrate temperatures are between 10C and 40C (49F to 104F) and your dew point is more than 3C (5F) below the substrate temperature. You can buy low cost temperature and humidity gauges that are accurate enough. There are plenty of free dew point calculators on the web. Working within this range avoids all the blushing and delamination etc. Cheers

[Robert Engel]

Thx guys, I'm glad I asked.

My gun has a 1.4mm tip. Will any or all of those mentioned work with this?

[Prashun Patel]

I've sprayed Enduro Clear Poly in my garage during the summer during humid times. It dried fine. If the conditions are fine for spraying shellac, they are fine for this product.

My bathroom and a couple dining tables for customers have been finished with this and i find it to be quite durable under these conditions.

It sprays and dries fast.

I think Arm R Seal, wiped on, is reported to be more durable - but (for the person with spray equipment) this theoretical increase comes at significant additional effort in application.

To be fair, I have not tried the gloss product; for high wear items, a satin finish appears to weather more gracefully than a gloss finish.

[John TenEyck]

Thx guys, I'm glad I asked.

My gun has a 1.4mm tip. Will any or all of those mentioned work with this?

The viscosity of both EM-2000 and Enduro Clear Poly is in the sweet spot for a 1.4 mm N/N in a typical gravity feed HVLP gun. You might have to thin Sayerlack AF55 a little to get the viscosity in the right range, but it should spray well, too. The other Sayerlack WB product, AF-71, has a much higher viscosity and likely would require more thinning than would be a good idea, but I've never used it so that's just a guess.

John

[Robert Engel]

I've had a comment on another forum about wb top coats affecting chatoyance.

Is this something I need to worry about QSWO?

Let me also say my plan is a wb dye, shellac sealer, sand, gel stain then top coat. I've done quite a bit of experimenting with various colors. An alcohol based dye actually seemed to augment the fleck better. I tried a Behlens Solar Lux but it was too orange and didn't pursue it. Any comments on wb dye vs alcohol?

I've put it off and now I'm down to the wire. I don't want to be all over the place with this so any an all help is most appreciated.

[John TenEyck]

I use Transtint dye which is soluble in both water and alcohol. With WO I favor using it in alcohol because it avoids most of the grain raising that can happen on WO when using WB dyes. I usually mix at least two dyes to get the color I want. Expecting to get the color you want with a single dye often leads to disappointment.

The comments you got about WB topcoats being bland, not highlighting the grain as well as solvent based finishes, etc. most likely came from folks who tried one WB product 20 years ago. There are many good WB topcoats these days that give great results, and should work well with your proposed finishing schedule. Look at Target Coatings EM-2000 and General Finishes Enduro Clear Poly.

One comment about your finishing process. I would be very, very careful about sanding the shellac sealer for fear of cutting through it into the dye layer. If you want to highlight the ray flecks I would sand after the dye has dried, then apply the sealer, gel stain, and at least one coat of finish before sanding again.

John