Water based clear finish question

[ian maybury]

Rustins from the UK do a water based clear acrylic floor coating http://www.rustins.eu/Details.asp?ProductID=42 which i find is great for getting a quick sealing coating on to workshop stuff. There's probably lots similar in the US. It goes on really easily with a sponge brush or a sponge, dries quickly, sands easily and is tough. In the can it's a cloudy whitish suspension - probably technically an emulsion. It doesn't have much effect compared to e.g. a polyurethane varnish in terms of changing/warming up the colour of the wood.

The one issue i seem to run into is that it's appearance is influenced by the state of the substrate. Not sure what happens, but it seems like it maybe doesn't penetrate/wet the wood to the same degree if there's something (not necessarily visible) on the surface to make it less absorbent - and the result can be a lighter coloured area. Likewise if there's even a very light film of glue.

It's a long shot, but has anybody else seen this with water based and found a fix? Shellac is probably a good alternative, but it's not all that readily available here.

[Andrew Pitonyak]

Are you able to get a picture of the difference?

Have you tried wiping it down with mineral spirits first to see if you can see anything standing out with that? Just curious.

[Lee Schierer]

The one issue i seem to run into is that it's appearance is influenced by the state of the substrate. Not sure what happens, but it seems like it maybe doesn't penetrate/wet the wood to the same degree if there's something (not necessarily visible) on the surface to make it less absorbent - and the result can be a lighter coloured area. Likewise if there's even a very light film of glue.

The condition of the substrate is the key to getting good results from your finish. Glue, oil, silicone or even finger prints can mar an otherwise flawless finish. You can usually spot these blemishes before applying the finish by wiping the substrate down with mineral spirits. Through sanding of the entire surface will usually eliminate the problem areas as well.

[Brian W Smith]

In cooking school........."Time & Temperature" will be one of your foundational skills.Well,along with humidity but,the student is hopefully going to get that as well.

In WW'ing.....Time,temperature(humidity),and surface condition applies.On hard to apply finishes(glues) be very critical of those three things.There are some ways to control them that will make a huge difference in whether the finish(glue)will hold up.

[John TenEyck]

As Lee said, wipe the surface with mineral spirits or alcohol before you apply your finish. You should be able to see any problem areas. Glue is a huge problem even if just a hint of it is on/in the wood in how dye, stain, or finish reacts.

John

[ian maybury]

:) An impressive level of agreement! Thanks guys.

I can't get a photo until tomorrow Andrew, but I've been seeing some small areas a couple of tones lighter than the rest. It's on some cheap ply workshop cabinets, which is more likely than natural wood to get contaminated anyway.

It seemed like it was a wetting issue, but (despite having encountered the same in the context of both adhesive applications and automotive spray painting - and the use of pre-cleaners) i didn't make the connection to using mineral spirits (white spirits over here) on wood. It makes sense in that the automotive variety smell pretty similar.

Sanding makes sense too - it presumably exposes fresh (unoxidated? - oxidation can be a big blocker of wetting even when brazing and soldering metals. Think it changes the electronegativity of the surface) wood, and opens up pores.

Sounds too like it's common to most wood finishes which is nice, as i quite like the product otherwise.

Makes sense too to broaden the issue to include bonding/adhesives use Brian - i saw that sort of thing often enough in industrial adhesive applications. Again though my inclination was to think (unthinkingly - there's lots of references about to the need to glue freshly cut surfaces etc) that wood is so porous that wetting shouldn't be an issue. Not so it seems...

Here's a long shot. Flame treatment (flashing an oxidising flame over the surface for a few seconds) helps to get adhesives to wet difficult surfaces like plastics. Wonder would it work on wood?

Google brought this paper up just now on the issue of wetting, and methods of improving it: http://www.adhesives.org/docs/default-document-library/surfaceprep_adhesives-org.pdf?sfvrsn=0

[Brian W Smith]

I've got to head to the shop but couldn't resist.

A well set up HVLP gun,and a really nice gun.....with all the stars in alignment WRT to our supply air,which we frankly take ridiculously serious.I can almost spray a big pce,a dresser.....in our living rm.Metal is different because the product "bounces" off the car,machine,whatever.Where wood it "sticks" from the get-go.But,diminishes as you build product.Wood is also way easier to control surface temps....product penetration....flow out.

[ian maybury]

Sorry Brian, I got side tracked. I've been thinking of heading down the HVLP route, but waiting for the requirement to clarify a bit - my woodworking is in a state of evolution.

On almost being able to spray in your living room - is this to do with the nature of the HVLP gun? I've not seen one in action. My workshop is small, and so far I've been thinking in terms of needing to set up a spray booth of some sort with extraction etc...

[Brian W Smith]

Ian,a cheap wind meter is very useful setting up whatever style booth(open side or enclosed) or area,for that matter.Try about 1-2 mph.The nicer units(Kestrel 2500 and up).....although way more expensive,have temps and humidity built in.I haven't done it,yet...haha,but they also have applications in DC world.The cheapies are less than 20$.

Transfer efficiency on the gun setup,very near laboratory quality air from comp.,and a clean/predictable air zone.The "booth" is only part of the equation.

[ian maybury]

Ta for that Brian. I'm more used to fully enclosed booths and compressor powered guns as used in the automotive refinishing context (or nothing at all by way of a booth as a kid when working in a garage), and have been trying to decide if it was worth building a DIY enclosed booth in the loft of my shop. The problem is that they need inlet and exhaust fans and get quite complicated and expensive. (pressure balancing, filters, ducting etc)

I've never been too sure how effective an open booth might be in comparison, although i guess that they must be good on extraction. Simple too - just a single big old axial flow fan. The incoming air though must be what ever is in the shop.

I won't be ready to go with anything for a while (still getting the area organised), but have some serious research and thinking to before then - and before committing to anything...