craters in my Poly finish?

Hi woodworkers,


This is a 24 mm Plywood (B grade poplar I believe) with solid oak 24 mm edges and rotary cut veneer on both side.
The dye is waterbase aniline.
I am having endless issues with this top. Already had to strip the veneer down once because I was sold rotary cut bookmatch oak veneer sheets. (I discovered that only one face is good the other cracks with such veneers)
I am using one part Poly varnish with the most decent "varnish brush" I have found here in Portugal (Forget about any quality tools here I have to import everything but sometimes you just have to do with what is around).
I sanded down with 400 grit (I only had this probably should have gone with 300), and I am having this horrendous aspect. the last coat already had done orange skin due to my attempt at using a sheepskin imitation roller but I sanded it down.
I diluted my poly with approximately 1/4th of PU thinner. I did nottice that it was extremely hard to apply and tacky (was it diluting the previous coat?).
I sanded with what I think is Silicone Carbide sanding paper and heard about sililcone contaminitation. Could it be the case?
I am quite desperate to find a solution as the amount of time spent on this piece has already reached "Legendary".
Attachment 453750Attachment 453751Attachment 453752

G’day Romain and welcome to the forum.

A little difficult to see from your pix but the surface appears to be very thick and has dried in a dimpled appearance. “Fish eyes” I have seen in the past tend to be larger and the new coat that has been applied moves away from any coat that was underneath.

Do do you have any silicone based sprays near where you are working?

Have you sprayed any silicone based sprays on machinery etc in your work area?

Did you scuff sand each coat before adding a new coat?

Did you use any form of sanding / pore filling product?

I think you answered your own question, rub it back and recoat. good luck.

That looks like classic silicon contamination to me
I would suggest you sand it back as far as you can.
Re apply your finish again.
But first remove any silicon based products from were you are working.
Also before re coating thoroughly wipe the surface down with thinners using two rags one to wipe on with wet one to wipe of with
Do not mix the rags up.
The principal is the first one pics up the silicon the second rag drys the thinners.
Put these rags in the bin when done,
It would also help to do this more than once.
Once your surface is clean don’t touch it with bare hands use rubber gloved hands from now on.

Silicon will stick to most surfaces most finishers will not stick to silicon.
What I think your seeing is your surface pulling away from the silicon(fish eyes)

Silicon is EVIL
Keep it out of your work space.
Hope this helps

Cheers Matt

If it is a silicone caused problem you can overcome it by adding an appropriate fisheye preventer. I use Smoothie for repairing cabinetry that has been exposed to spray furniture polish. There are different types of this product for different types (oil or water based) of finish.

Attachment 454788

Silicone.

Man that is great stuff - but in the wrong place it is pure evil.

Silicone is the dreaded curse of the automotive refinishing industry. They use fresh wipes and a product like this immediately before spraying: De Beer Silicone Remover 1-951 5Lt

Grab a small bottle at any auto refinish supplier.... and some "tack rags".

I also tend to wipe everything down with Isopropyl Alcohol (100%) i.e. rubbing alcohol. It instantly removes greases and contaminants and evaporates in seconds. It also doesn't raise grain. This is where I buy: https://www.sydneysolvents.com.au/is...ol-100-5-litre .... also good for tidying up residues, glues, removing stickers, cleaning, disinfecting... its almost magical in its breadth of usage.

Though you'll want to test that aniline dye first. Being water based it shouldn't affect it, but anilines are usually alcohol based..... where did you get yours? I'm on the hunt for some bulk anilines!

With the poly, let it harden a bit and "rub it out". Sanding it smooth is the first start, but those bubbles and contaminant-dots will drive you crazy. Take it easy, sand with 120 grit. You only need to take the tops of the ridges off.

With your finish, looks like you've put it on very thickly. Lots of thinner coats is the trick. They will dry very quickly if its thin. Thick poly takes an eternity to dry - if it ever does. If you can get you hands on a spray gun (borrow one and a compressor?) it will make the job much easier. Otherwise, a wide soft brush is fine. No need for "fancy".

Have no fear in thinning it if it the day is hot.

Watch/read these:
https://www.woodworkersjournal.com/r...h-satin-gloss/
https://garyweeks.wordpress.com/2011...arnish-finish/
https://www.popularwoodworking.com/p...h-poly-finish/


Keep us updated!

Spray teflon products cause fisheyes too.

rather than chasing illusive surface contamination issues, look first at the cracks that are in all rotary cut veneers.

These cracks go the full depth of the veneer and can suck up large quantities of finish.

My personal solution is to use a matching sanding sealer to the finish coat to choke out and stabilise the surface before even thinking about a top coat.

I have used things like putty style grain fillers, but they are not as effective as sanding sealers, in getting deep into the cracks and staying there during the sanding process.. ... the putty style fillers will also tend to dull the grain and feature.

I have worked a lot in plywood, and have found I often need to use 2 or 3 coats of sanding sealer, before I have a reliable smooth, flat, crack free surface ..... and yes you need to sand right back between coats, until the cracks are filled.

I will usually thin out the first coat of sealer so it is good and runny and gets right in.

Brush is by far the best and at least in the first coat or two, work the surface hard with the brush to push the product into the cracks.

unless you are spraying, a good quality brush, well used is your best option for applying the top coat.

warming the product and thinning ever so slightly will help the finish flow out.

cheers