Sealing MDF board

[Peter Wildman]

I make small items . Dolls cots Toy garages using MDF board . We call it supawood in South Africa . I would like to know an effective way to seal the cut ends from just absorbing coat after coat of spray paint . Hand painting the ends is laborious and leaves runs on the smooth surface . is there a mixture I can rub on ?. No water based product as end immediately swells .

[Arron]

Spackle, wallboard plaster or whatever else you want to call it works well.

[woodPixel]

Being in SA I'll not mention brands (that would be useless) for purchasing, but so you can look up their properties.

There are 4 main ways of doing this.

-- A proper tricoat paint. It acts as a sealer, undercoat and sandable base. Haymes TriCoat is the product I use. (1)
-- Car bog. Ordinary crash repair filler from SupaCheapAuto. Put it on with your finger, wait until it is "green" (i.e. before it gets fully hard) and shape it. Sand it to shape/size once fully hardened. (2). Car Bog is what professional speaker installers use in the auto industry.... all auto speakers are made of MDF and presentation is critical.
-- A home made recipe of either: watered down titebond glue painted on, shellac (it dies well, fast, is hard and sandable) or a product called "MODpodge" which dries quickly, dead smooth and sands reasonably well.(3)
-- Drywall compound. The fine finishing paste that comes pre-mixed. Use the "finish" or "topping" one, it is very fine (4)


Above is my order of preference. I use MDF a LOT.

The car bog is good for shaping, fixing mistakes and making speaker bodies. The Gyprock Topper is bloody excellent and does an outstanding job.

All these methods will give you a dead flat, dead smooth surface (after sanding) to apply either an undercoat or the final topcoat to (for #1).


(1) Product Information - Haymes Paint (http://www.haymespaint.com.au/products/product-information/view/Elite%20Tricoat%20Primer%20Sealer%20Undercoat)
(2) SCA Lightweight Body Filler - 500g - Supercheap Auto (http://www.supercheapauto.com.au/Product/SCA-Lightweight-Body-Filler-500g/287584)
(3) https://www.spotlightstores.com/craft-hobbies/basic-craft-supplies/glue-adhesives/glue/mod-podge-matte-glue/BP80078525001
(4) https://www.bunnings.com.au/gyprock-csr-15kg-easy-finish-topping-compound_p0736156

[Fumbler]

I have found sanding with power sander, either Random, ROS, palm sander, or painstakingly hand sanding. I have found that power sanders generate frictional heat and thus melts the binding product in the MDF to then become as sealed as the face of an MDF board and wont soak up ay paint. give it a crack.

[justonething]

Being in SA I'll not mention brands (that would be useless) for purchasing

I thought that's not being very nice to South Australians. And then I look at OP's location...... SA can mean so many things......:doh:

[Peter Wildman]

Thank you all make sense never thought to go the body shop route . will try to get the equivalent in ZA .

[Peter Wildman]

Sorry have a son in NSW so know the confusion . ZA