Surface Curing Issues...Please help!

[marlon]

Hi! Everyone, wonderful forum you have here.

I wonder if anyone can help me.

I want to make a basic shiny black center table from mdf with a hard finish. I thought it prudent to practice some finishing techniques on scrap peices before I move forward.

There seems to be a problem with curing to a hard surface (ie.. weighted objects leave depression contact marks) with every product I've used so far. I have of course sealed all practice pieces with a white mdf sealer before finishing product attempts.

1. Black Matt paint(high voc) applied with foam brush allowed to dry for longer than the specified 16-24 hrs followed by light sand flat prep & clean then a top coat of water based indoor varnish(low voc) (Wickes).

Result: Even after a week it never cured (ie.. weighted objects leave depression contact marks).

2. Black Matt paint(high voc) with foam brush etc.. then top coat of Johnstone's woodworks clear gloss polyurethane varnish(high voc)

Result: Even after a week it never cured (ie.. weighted objects leave depression contact marks).

3. Black Matt paint(high voc) applied with foam brush etc.. then a top coat of water based acrylic floor lacquer(low voc).

Result: Reacted with the paint (peeling effect).

4. Tried mailee's described CD Rack posted method and even though the surface dried to a nice gloss after the 2 days as he stated, I still ended up with the same surface contact problems. Good method however for wardrobes and siding type items. I also tried to top coat this with the water based acrylic floor lacquer as is water based also but got a cracked looking reaction.


In summation:

All attempts to produce a hard high gloss finish thus far have resulted in a surface which behaves unfavorably to weighted objects.

Does anyone have any helpful suggestions as I don't know what to try next?

Ideally I would like to use low voc products for the top coat as It would be safer for use with my spray gun(non hvlp gun).

 

[wizer]

Welcome Marlon. Can I ask what the weighted objects are? Cups, Plates, etc? Or much heavier?

 

[marlon]

Hi!

Thanks for the interest.

Weighted objects being .. Like a dvd/vhs recorder type weight.

 

[DaveL]

Hi Marlon,

Welcome to the forum.

I don't have an answer to your problem, but another question, what you you standing on the test finishes that is leaving the marks? Maybe you need to add a mat under it if it is very heavy with small feet?

 

[marlon]

If it helps anyone in their thinking....

I did apply the water based acrylic floor lacquer directly on the mdf sealer itself and that seemed to dry to a good hard finish quite quickly with no visible marking. However I don't know of a black paint that would be reaction free when top coated with the water based acrylic floor lacquer.
Anyone know of one?

 

[mailee]

Hi Marlon, I assume it is MDF you are painting, if so you may find it is the MDF primer/sealer that is to blame. This never really dries hard in my experience and allows the top coat to 'sink' with weight. If it was me finishing it I would use cellulose sanding sealer, followed with your colour and topped off with a two pack laquer. Unfortunitely you state you do not want to use high VOC products in which case I would say use Spirit based sanding sealer but allow more drying time followed by your colour and top it off with Rustins plastic coat. This should give a good hard wearing finish which will not mark. Even my Computer desk shows signs of marking with the weight of my printer and scanner on it, (slight but still there.) For a really hard finish you need something that cures with a hardener more like an epoxy than a paint. HTH. :wink:

 

[Ironballs]

There are many that feel that a water based lacquer never cures as hard as the cellulose types and even with cellulose you have to give it an appropriate period of time (and some warmth) for it to cure properly. I'd follow Mailee's advice and make sure you allow enough curing time - could be up to 3 weeks

 

[marlon]

Thanks for the suggestions mailee. I really didn't anticipate the need for such specialized materials for the top coat of a table. Definitely have a lot to think about now.... Man! 3 weeks cure time. :shock: Iballs, thanks for the heads up.

The 2 pack lacquer option as you say would probably be the best option if I had a proper spray booth. Though I could probably get a good top finish with a foam roller/brush if I'm careful. The plastic coat (£16.03/1L from AGWoodcare) option seems good as well if ends up being the more price+compatible option.

Is there a particular 2 pack I should go for, that is ideally suited for my needs and where can I get it from?
I could only find these:

Decorating AGWoodcare.co.uk:
Junckers Professional 625 Acid Catalysed Lacquer(solvent-borne) (£35.29/5L)

Wood Finishes Direct.com:
Two Pack Lacquer(water-borne) (£39.10/2.5L)
Acid-cat Lacquer(solvent-borne) (£40.76/5L)

Also before I make my final choice is there a top finish that I could use that would dry to a hard finish if I chose to make the actual table top part out of something with real wood grain, say block board or other?

 

[wizer]

Keep posting your results marlon, I am interested to hear what you find is the best solution. I have a coffee table coming up that could do with a bullet proof finish

 

[JonnyD]

I would reccomend getting a pigmented lacquer rather than painting black and clear coating the lacquer. The pigmented lacquer has various sheen levels from 10% matt to 90% gloss. It is designed to be spayed but i think it could be applied with a roller and then polished out using a cutting compound such as farecla. The pigmented lacquer will give you a deep gloss finish after it is burnished and be rock hard after its cured. You can get it precatlysed or 2 pack acid catylsed which is slightly harder. I personally use http://www.morrells-woodfinishes.com/ and they have depots accross the country.

jon

 

[Chris Knight]

Really, high finishes (think pianos) are finished these days with polyester lacquers - like those referred to here http://www.londonpolyester.co.uk/ They are however more for commercial use than amateur.

 

[mailee]

I would agree with Jonny and go for the pigmented laquer. Only thing I would add is that to finish off once it is hard use some 1000 grit Wet N Dry used wet to level the surface and then polish up with the
Farecla for a smooth as silk finish. HTH. :wink:

 

[Gitface]

Hi

This might not be anywhere near a raditional way of doing things, but if all you are after is a hard shiny finish then you could try using glass fiber resin with out any matting, just the resin, and a cheap pot of black acylic paint from a modal shop.

This would need to be sanded the usall way but might work out cheaper.

Just an idea, might not work as intended and you might have to do one surface at a time to avoid runs, but with an average cure time of 30 mins or so it would not take long to do a table.

Mark...........

 

[marlon]

Thanks for all the suggestions... It's been very educational.

I got soo despondent with the regular products like water based varnishes and the regular polyurethane stuff that you guys have really set me straight.

Keep posting your results marlon, I am interested to hear what you find is the best solution. I have a coffee table coming up that could do with a bullet proof finish

JonnyD's suggestion of a 2 pack acid catylsed Pigmented variety was spot on. The stuff is made to order so took a little while to obtain. Man! this is hard ass stuff and cures very quickly indeed. :shock:

I’ve tried some test pieces with a paint brush and it performs very well indeed. Obviously spray application method if I had a spray booth would produce ideal results however a paint brush (with proper P3 Filter Gas & Vapour mask + good ventilation) works pretty well if careful.

I followed mailee's suggestion except I used P1200 si carbide wet sand paper followed by some liquid TCut (I had sitting around) plus some elbow grease produced a nice finish. A better gloss finish would be produced with some form of machine buffer action. Is purchasing a drill attachment polishing kit a good option or would something like a Direct Power 120W 230V Auto Polisher(£19.57 @ screwfix) be any better or perhaps some compressor tool attachment I could use?

Only problem I have on test pieces now are the light sanding scour circular scratches that are visible beneath the high shine. Perhaps the P1200 silicon carbide wet n’ dry sand paper I used was not fine enough. Anyone have a solution/method to eliminate this?

Also any particular Farecla I should get… G10?

 

[Chris Knight]

1200 isn't that fine a grit when it comes to polishing a finish. You can get far finer polishing materials such as those used for polishing aircraft windows, etc. For an immediate cost effective solution, try Abralon 4000 grit.

 

[wizer]

Thanks Marlon. Got a pic of the finished result?

 

[colin taylor]

Just a thought. Rustins two-pack "plastic coating" lacquer is pretty bullet proof and brushable too.

 

[John. B]

Does it have to be painted? :-k is it not possible to glue on a black laminate with a suitable backing then edge with a contrasting timber :lol: :lol:
That way you will have your shiny black which won't indent and easy to clean.

John. B

 

[miles_hot]

Only problem I have on test pieces now are the light sanding scour circular scratches that are visible beneath the high shine. Perhaps the P1200 silicon carbide wet n’ dry sand paper I used was not fine enough. Anyone have a solution/method to eliminate this?

To get rid of these swirl marks you could look to various car detailing forums which will be able to give you lots of ideas for products which can be worked by hand or by machine...