Red Gum Finish

[RETIRED]

An email that I recieved today:

Hi ,

Saw your response on a woodworking forum and figured you must be an
Aussie, so thought I might ask you a question which the yanks cannot
answer. I am building a 50mm thick table with cured Redgum and filling
the knots with a black epoxy to give a high contrast finish.

I was thinking of using an epoxy on the table top as well, but have
lately been a bit dissuaded by claims it "isolates" the timber from
touch . Any brilliant ideas for finishing Redgum? Is Danish oil a
viable option to produce a high gloss finish?

Thanks in advance, sorry for the interruptus!
Name and address removed to protect the innocent.

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Ian () Robertson
"We do good turns every day"






[This message has been edited by (edited 12 November 1999).]

[Shane Watson]

Finally I get around to replying to something! Stupid putors

Theres a heap of different finishes available for you to use. I wouldn't suggest epoxy, but it is an option.
It really depends on how you can apply a finish, I mean if you havn't got access to spraying facilities then some good finishes are out of the question or are going to be harder to use.

I would use a lacquer, an acid cat. lacquer. this can be rubbed back to match most finishes and to any gloss level. It is also resistant to 90% household chems. Would apply it using spray so as to obtain an even surface. Although it can be applied by brush or rag( rubber ).

As I said above there are many different options, this is just one that I would use, others will have different opinons. Hopefully they will fill you in on there's and you can go from there!

Cheers
Shane!!

[Marcus]

Hi Shane,

Thanks for the tip, seems that an oil/wax combination produces a pretty good looking result but the durability is questionable so perhaps the lacquer approach is better. Can you suggest a brand/precise type? I can get access to a spray gun...

Marcus

[S Hayward]

Don't forget.
When applying a finish to a top it is most important to cover both sides equally. Three coats of laquer on the top and a so called "sealer" coat on the bottom
will create an imbalance in the way the wood breathes. Usually this results in some mild to serious cupping. We supply kitchen bench tops and this is the most common problem encountered.
Regards
Shaun

[Shane Watson]

Marcus.

There are more brands than there methods! Again everyone will have there own likes and dislikes.
I use Mirotone 830/30. But if you want gloss then you would just use 830. This is my preference which works great in my climate. I might suggest you phone round some of your local furniture manufacture's and ask what they use, this will give a better idea of whats better to use for your local climate etc.
As Shaun said, it is important to get a good even coat on the underside of the top! I too have seen and repaired many tops and counters etc that have had little or no ( ! ) coating on the underside. I myself don't match the amount of coats both sides ( eg, three coats on top & Three coats on underside ) But I do ensure a good even coverage and I have never had a problem.

As for wax finishes, these can be great and if done properly will have little difference to the look of a lacquered finish ( although there are huge arguments about this, but note, I said done properly ) But for table tops there is a huge advantage going for lacquers, even polyurethane. But thats another story
HTH!!
Cheers
Shane...

[Mac Simmons]

Hey Mates,

Our climate, is much different then it is down under.

You do not find furniture "coated" on both sides in the USA.

Most coatings including waxes, except for some of the super catalyzed coatings are pourous enough to allow the moisture to both enter and also leave the coatings. this transfer also would apply to the uncoated woods.

How important it is to "coat both sides of the wood" (timber) maybe more important in certain climatic conditions? In some other cases it just maybe a waste of time, and your material.

(It may look, and sound better when selling the job, then it will do in preventing warpage, or expansion and contractions in the woods)

G'day

Mac


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[Shane Watson]

Hi Mac!

Coating both sides ot the top is important. but your right, it has a lot to do with climatic conditions. And also personal preference. I know a lot of local people that don't seal both sides, but I know as many if not more that insist that its done.
I really don't know the scienctific answer but I am sure there is one out there
Personally, I do coat both sides, but I don't put equal amounts, I don't believe that is neccessary.
But as I restore a lot of antiques I can also say that most pieces I restore that have tops and large ones at that are not coated both sides and are still as flat as they were when they were made!
I really think it comes down to the type of finish you use. Catalized lacquer's and polyurthane etc don't really allow the timber to breath so if both sides aren't coated then the uncoated side will do all the breathing.... Eventually having to give way hence the cupping, shrinking, expanding etc that can happen....
Whadya think??

Cheers

Shane!!

[ubeaut]

Hi Guys

Good discussion. In my experience to leave one side of redgum uncoated would be to almost invite disaster by means of warping and bowing etc. I reckon red gum would have to move around more than almost any other timber even if it has been dried for 100 years.

I have also found that different timbers will react differently in the Oz conditions. English and American Oak antiques can literally explode when brought into our summers. Cedar antiques are very rarely coated both sides and seem to stand up to the conditions quite well etc. etc. etc.

One little note to those not in the know. Never coat the inside of a bookcase. Leave the timber raw. This will stop mildew etc. on the books.

Thats my little bit.

Cheers
Neil

[Mac Simmons]

Hi Shane,

In different parts of the countries there is completely different temperatures, and moisture conditions.
As I mentioned most coatings are pourous enough to allow the air exchange to come and go ( as all coatings are not equal in this characteristic, the transfer will be greater with some coatings then in others) Polyurethane coatings is also pourous as they will also allow silicones to enter the pores, where the two component catalyzed coatings will not allow penetration.

The only time I ever coated both sides of the woods was when I replaced a section or part of the furniture because it had warped.

I say, do what ever you feel will work best for your work in the long run.

G"DAY

Mac


------------------

[knuckles]

Mac

You obviously have not ever used Redgum. It would not be wise to leave the under side uncoated. As Mr Neil says, "It would be inviting disaster." I will bet that there are many people out there who can substantiate this fact.

You are right about the finishes being able to let the moisture in and out. However, if one side is not coated it will suck in the moisture dramatically whilst the coated surface will let it in very slowly, (almost not at all) thus creating a cupped piece of timber due to the expansion of the uncoated and now moist side of the timber.

A simple experiment with moisture will prove this to you. Coating all surfaces with an even number of coats will allow moisture to penetrate at a more even rate all over and should control the amount of warping etc. This is plain old common sense, not scientific fact.

Knuckles



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Don't mess with me! I know where yez live and I might just pay yez a visit. Capish?

[Mac Simmons]

Capish,
Don't come alone....

If it take the same amount of coats on both sides to keep it from warping, so be it.

As there are many different coatings that could be used that would allow the moisture in and out evenly.

Why not just use a coating that the moisture will not penetrate.

Now, that is common sense.




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[S Hayward]

But wait, there's more.
Len Fischer from the Woodcraft Guild of the ACT published an article on finishes and their ability to provide a moisture barrier. It was interesting to see the differences between various types. It was, as I recall, an extract from some other mag but I believe the info to be based on sound technical fact. If I can dredge up a copy I will post it.
Sorry Mac, but the only type of coating that wont let any moisture in is a two inch layer of epoxy. Those who specialise in this kind of bastardisation of fine or not so fine woodwork ought to consider another occupation/hobby. Purely an opinion here of course. Why not appreciate the medium with which we choose to work and let it be. In other words, if it wants to move, as it will, then let it go. Just make sure the design allows for this. As for it not being necessary to coat timber both sides in some parts of the world but essential in others, I don't entirely agree here. Firstly, in a mobile society you never know where your work will end up. The conditions will change. Also, where in the world does humidity stay absolutly constant? I agree that some areas experience greater variations than others but almost everywhere experiences some variation from week to week or month to month. If you are going to offer guarrantees on your work you need to account for as many variables as you can. I believe in covering your rear as much as you can in this litigious age in which we live. I also hate having to go back and fix problems. Best to avoid them in the first place.
Wow, isn't woodworking an interesting game?
Cheers
Shaun

[Shane Watson]

Mmmm. Macs right, do what you feel works best! Like I have said before, I know of people locally who don't coat both sides. Do they experince more problems than I do?? Who can really tell.
But if a client came to me and asked my advise I would advise a coat both sides.
Theres also evidence that the secureing system of the top to the base can cause problems. Timber moves! It a simple fact, as timber is alive even in death!
I still don't believe that equal coats both sides are required, look at it this way - Is a professional going to spend the time neccessary in coating, sanding, coating, sanding, coating both sides equally? Not unless they can afford to loose profit! I can't! Unless you coat and sand the top and underside equally, there will be very different amounts of coating between the two sides. And I don't think I have seen an underside of table finished like the top yet. No matter how high the standards of workmanship.
How us aussie's do our work will always more than likely be different to the rest of the world. Thats what makes us Aussies But its not neccessarially better than anywhere else.
It really does come down to your own methods. We can all advise, but in the end its always our own choice, and our mistakes will always teach us more

Cheers

Shane....

[RETIRED]

Well, Marcus you really started a great debate with your email to me.

I finish both sides equally with the finish I use (mainly N/C lacquer) and yes, Shane even table tops, just fished some chairs and the seats, which are detachable were lacquered equally top and bottom with 3 coats.



------------------
Ian () Robertson
"We do good turns every day"

[S Hayward]

Can't quite let this one go yet! Ever slipped a hand under the dining table between mains and sweets, when the conversation has turned to something less captivating than table finishes, and discovered the underside feels like a bit of 40 grit? This is an incredibly disappointing moment when you have been quietly congratulating the maker for a job well done on table then the very object of your praise rips half the skin off your fingers. If you don't intend to polish the bottom, or are only going to give it a rough coat, please cheat a bit and polish well at least 250mm in from the edge. ( 10 inches for our US friends )This way the dinner guests can only complain about the food.
Bon appetite
Shaun.