Ironbark benchtop finishing issues

Hey guys. First post and, of course, it's a plea for help!

I'm making a few benchtops out of recycled Ironbark (100 year old roof beams from a warehouse). All slabbed, sanded, boltholes and natural splits and gaps filled with West Systems epoxy. It's time to start finishing and I took advice from a local furniture maker and ran a first coat of Cabothene. Unfortunately, this isn't penetrating the timber at all. 36 hrs after the first coat and it peels away from the timber with a fingernail. I don't think sanding and recoating is likely to help, so it's time for a reboot.

I suspect the reason the timber isn't taking the varnish is latent oil content in the wood itself. If I sand it and leave it for a week under a drop sheet (which i've done several times) it changes colour (deep reds start forming), except in any areas where there's direct contact. It seems like it's oxidising or that the timber oils are leeching out???

I've been trawling the forums here and it looks like Feast Watson Floor Seal might be the go instead of the varnish. I'm just worried they won't take on the epoxy fill I've used and wondered if anyone had any suggestions.

So what do you say guys? Natural oils or does the epoxy mean I have to go with a 2pac marine grade finish? And if the varnish wouldn't penetrate the timber, will either of these?

Here's a shot of the bathroom bench with the epoxy filled gaps showing here as dark areas (they're actually lovely and transparent)
bench01 | Flickr - Photo Sharing!

Any suggestions would be greatly appreciated.

Thanks,

Obelisk8

Mate,

the only thing to use in this situation is Mirotone! It works very well with oily timbers.

Not a promo, just the facts, check out their website, spray on and forget! Good shyte!

Regards,

Oddjob1

Hard Shellac should stick to it like poop to a blanket. But get rid of the poly before you use anything else. Shellac will stick to pretty well anything. If that doesn't work then pretty much nothing else will.

Cheers - Neil :U

PS Give the timber a good wipe down with metho before applying any finish, this will kill the oiling on the surface and help whatever you put on to stick. It would be interesting to get a deep probe moisture meter on it to find out the moisture content. Have seen some of hat stuff well over 100 yrs old with more than 20% when tested with deep probe.

Thanks for the responses guys! Great stuff.

Neil, I got a moisture probe in there when I picked up the timber. It ranged between 9 and 11%, which I thought would be ok. That hasn't stopped it changing shape a little though. I think it's largely because I've been working in an open carport near the coast over about 6 months (time poor, shedless beginner and a very slow worker).

I've got 3 benchtops on the go and I've been learning heaps, mostly by making mistakes (not alternating shrinkage on plain sawn boards on one, trying to clamp warped boards flat on another, etc). Think I've corrected most of those problems now though.

I think I'll have a go with the Hard Shellac and maybe follow with Trad Wax. Just watched a bunch of instructional vids on youtube and it looks like fun.

How fine should I go with sanding before I start with the shellac? Prior to trying the poly, I sanded 40, 80 and 120. Should I go further?

Thanks again,

Obelisk

OK. Finally got back to this. I used a 1:8 hard shellac first coat to seal and after a quick sand I'm 3 coats down on the underside of the benchtops. So far, it's looking fantastic and seems really robust.

As a test, I sanded back through the grades to 400 grit (based on Neil's finishiing vid with my new ROS, or Ross as I like to call him) and I reckon that's about all I'll need given how "featured" the timber is (bolt holes, cracks etc... all filled with west systems epoxy, but still pretty rough looking). All feels amazingly smooth. Not quite Grand Piano, but not far off.

After a couple more coats on the undersides, I'll flip them, strip the poly and start working the finish into the tops. The question is, how many coats of the Hard Shellac, do you think I'll need to produce a hard waring finish for built in benchtops like this?

I'm using a pad and airplane, glide on, glide off approach, sanding lightly at 400 grit between coats. One bench is for the bathroom under the sink, and I'm particularly concerned that I get a good seal and moisture resistant finish for it.

Appreciate any advice. This stuff dries pretty quickly (especially when it's 35+ like today), so I'm no longer scared by the number of coats, but don't want to undercook the job. It's kind of irreversible once it's fitted to the masonry.

Cheers,

- O

Alright. The undersides are done and dusted. Only five coats of the Hard Shellac as they really just needed to be sealed. I thought I'd take it as an opportunity to take the shellac for a roadtest though, before starting on the tops and front edges.

benchtop finishing detail | Flickr - Photo Sharing!

This lovely feature will never see the light of day, sitting as it does on the underside of a fitted desk. The shellac is really bringing up the character of the timber. And, although, there are still plenty of hairline cracks, veins and a few divots, I reckon they'll come up pretty well.

Here's a shot of the three in my luxuriously appointed woodworking shop

benchtops in the "workshop" | Flickr - Photo Sharing!

Based on the underside tests, I reckon I'll need about 10 coats on the tops. Does that sound about right to you more experienced woodies?

Cheers,

- O

I would take the sanding up to 600 for top. Using a pad will probably put down less shellac than a brush but if you use a brush you need a really, really good one like these from Gramercy Tools


This little video of a brush being made is definitely well worth a look. Click Here

With one of their 3" wide brushes I would do the following: Cut Hard Shellac 50/50 with industrial metho, then cut halt of that 50/50. 2-3 coats of weakest mix, same with medium mix then a final coat of full strength. Do it over a few days and not in wet or really humid weather. Final coat (with the good brush) should almost look like glass.

Use long straight strokes with the gliding off thing happening and just barely overlap the coats. Don't splash it on like it's paint.

I have only padded it with a French polishers rubber applying it as I would any French polish so can't really comment too much on the padding you are doing. But using the good brush as above the finish was almost as good as any full blown French polish job.

Hope this is of some help.

Cheers - Neil :U

Thanks for all your help Neil. They're finally done and ready for the cabinet maker to install. And the finish from the Hard Shellac is awesome! Will definitely be using that again.

IMG_1865 | Flickr - Photo Sharing!
IMG_1866 | Flickr - Photo Sharing!

I'm going to grab another bottle to give him, so he can run a final top coat once they're trimmed and the holes for plumbing etc are cut.

Appreciate your help.

Cheers

-O