MDF CNC Router plans / parts for home build beginners

[Zephyr]

I have a suggestion about sealing MDF.

As most of us know from experience (there are a lot of MDF 'bananas' around), MDF is hygroscopic and will absorb moisture from the air. If it absorbs water from the air unevenly and/or the MDF sheet is not a uniform thickness it will warp. Sealing it all over against moisture absorption could be the answer to preventing it warping.

One sealant could be plain old boiled linseed oil which, if put on correctly will polymerize like plastic and it’s also a little flexible as well. It's also cheap.

Clean the dust of the MDF. Round off any sharp corners if possible.

The first coat can be boiled linseed oil diluted 50:50 with turpentine or white spirit put on fairly quickly (to prevent warping). Wipe it on with a cloth and leave to dry (supported on blocks) in moving air away from heat or direct sun.

2nd coat can be 75% boiled linseed oil 25% turps. wiped on quickly with a cloth. Don’t leave pools or surplus on the surface - they won’t dry properly and won’t polymerize.

These 2 diluted oil coats will go into the MDF and provide a better key for the next coats.

Next use neat linseed oil wiped on with a cloth and again taking care to remove any surplus. The MDF should then be fairly well sealed but the more coats you put on the more effective and long lasting the seal will be. 3 or 4 more coats at least of neat linseed oil wouldn’t go amiss.

I know it’s time-consuming but people without much money to spare would rather spend their time and it’s low tech.

Don't seal moisture inside damp MDF. Make sure it's as dry as possible and the ambient air isn't humid either.

A very light sanding with fine glass paper between coats will help to key the coats but vacuum-clean the dust off.

Remember safety. Wear rubber gloves, don’t breathe in the fumes or dust, dispose of oily cloths safely - either in a bucket of water or wash them out thoroughly and dry them outside. Oil-soaked cloths are a potential fire hazard.

I'm not suggesting you try this on an important or complex part. Try it on a test piece first.

I hope this helps and that I'm not 'teaching people how to suck eggs'. Let me know if I am and I'll shut up. If anyone tries it I'd be interested in how well it worked for them.

Regards.