mineral oil over nitrocellulous on mango desk

[lukerohde]

Hi All

I purchased a lovely kiln-dried mango-wood desk. I read that without maintenance, mango is prone to drying and cracking in dry climates with heating, particularly near radiators. I live in melbourne and have central heating.



I read to maintain it by rubbing in mineral oil a couple time a year. To keep applying till it stops soaking in, leave it 20 mins, wipe off the excess, then leave it to dry for 6 hours.

I did this and it took up a lot of oil and seems beautiful - richer grain. Then it occurred to be to enquire about what kind of finish it had already. The shop told me it has a nitrocellulous finish and doesn't need oil or any maintenance.

I'm surprised it soaked through the lacquer. Mineral oil is non drying, so it must have soaked in.

I'm wondering if I have dissolved the lacquer or caused myself some other pain.

Is oiling mango a bad idea when its been finished with nitro? Or should I keep it up if it appear to work?

TIA
Luke

[Arron]

Hi Luke.
No-one has responded because you’re in uncharted waters - putting oil over nitrocellulose lacquer. I’ve never heard of someone doing this before.

I think the advice about continuously oiling the mango for maintenance refers to unfinished or oiled mango. Yours is already finished with a relatively impervious coating and looks to have some effective grain filling too. Therefore I wouldn’t do it as its unnecessary and possibly detrimental but at the least it’s unnecassarily risky.

If you find the surface dulls over time buff it up with some automotive cut and polish - rubbing hard with a cotton rag.

BTW, most furniture manufacturers stopped using NC lacquer a couple of decades ago. Most now use precatalysed lacquer (which is derived from NC) or conversion varnishes or 2 packs. I just mention that because it might indicate the salesperson wasn’t fully informed about the finish - it’s hard to understand why NC or any of these other modern clear finishes would take up oil ‘liberally’.

Cheers
Arron

[lukerohde]

Thanks for the tip Arron. The underside of the desk feels raw to the touch so does inside the desk. Should I oil that? Or since its not a work surface would one normally not bother - I'm mostly concerned about the timber not being dried properly coming from a high humidity climate.

IMG_2141.jpg

[Arron]

The conventional thinking here is that finishing both sides of a board in the same manner prevents differential moisture loss, so minimises warping and cupping.

In that regard, if one side is lacquer and you oil the other side then you haven’t achieved that goal because both finishes have different tendencies when it comes to moisture transfer. I guess it follows that the best option is to nc lacquer the inside. That’s a bit hard to do without a spray gun and some experience, so the next best thing is probably a polyurethane varnish - which should have similar properties to the nc.

However, most commercial furniture is not finished where it can’t be seen and it seldom seems to cause a problem. I don’t really have experience here because I always finish mine inside and out.

[Christos]

There is something else that needs to be considered.

How accurate/knowledgeable is the sales person concerning the finish that was applied. As mention above why would it soak in so liberally.

[woodPixel]

You know, this looks remarkably like furniture made by Green Cathedral: https://www.instagram.com/greencathedral/ and Green Cathedral Furniture Noosa - Modern Australian Furniture Design

He is in Queensland. The legs are ABSOLUTELY his style and the mango.... local en masse.

[lukerohde]

"finishing both sides of a board in the same manner prevents differential moisture loss, so minimises warping and cupping ... so the next best thing is probably a polyurethane varnish" This makes great sense and is the advice I've been looking for. Thanks Arron

My sisters 5 year old mango table is unfinished on the underside, is warping and split.

It's just a mass produced OzDesigns piece. I got the NC info from their head-office but I doubt they really know or care, so long as it survives warranty.