Spraying water based gloss

[Corset]

I have been experiment with spraying some Wickes water based gloss onto MDF with an earlex HVLP system. I have coated with two coats of primer with a roller.
After some trial and error i have been spraying the gloss at 20% dilution which has gone on great and looks good. However......... after two days the first coat is stilll tacky to the touch. Is this because its ready for another coat? or Has the mix been too diluted or is something more basic wrong.
Aby suggestions greatfully received as I want to spray another coat tommorrow and need a plan of attack.
Owen

 

[Steve Maskery]

I don't think any finish should still be tacky after that long. What does it say on the Data Sheet? Can you dilute it that much without affecting the chemical properties? It sounds a lot to me.

I shall follow this with interest as finishing is not exactly one of my strong points.

Cheers
Steve

 

[mailee]

I have used the Wickes water based gloss myself Owen but I didn't thin it at all. It did take a day to dry and I then left it another day to make sure it was hard enough to polish. I think maybe thinning it is the problem. Mine was on MDF too. HTH.

 

[George_N]

I've sprayed a bit with water-based paints onto MDF. I usually use MDF primer followed by undercoat and satin or gloss top coat and all of these paints are sold as quick-drying. My experience is that they do dry quite quickly and, depending on conditions, can be re-coated within an hour or two. Although they may not be completely cured after 24 hours they are certainly not tacky to the touch. I use a B&Q HVLP sprayer and dilute my paint with tap water until it will run through the viscosity cup in about 60 seconds. I can't think of any reason why adding water would make the paint slower drying. How heavy a coat are you spraying?

 

[Anonymous]

You may have a problem with humidity, coupled with overthinning (20% sounds rather a lot). Give it another day and see how it is.

 

[Corset]

I will have a look at it again tonight. I cannot see how a 20% dilution can make that mich difference, but as i am clueless I will try a thicker mix and see how i get on.
Owen

 

[Tusses]

maybe there is confusion - ?

by 20% , I take it you mean 80% Gloss 20% water ?

I have heard that you need an air flow over the work for it to dry properly ?

 

[roombacurious]

I've had similar problems with finishes, esp. varnishes when the piece had been left to cure in my damp shed or outside. Humidity seems to ruin some finishes when curing.

A while ago I tried finishing a wooden slide with varnish hoping it would make it really smooth and slippery. In fact, the varnish never really cured as it was autumn and the slide was in the garden. Instead of slippery it ended up really sticky and never improved.
My solution was to plane the vanish off and use oil instead - I don't know whether there is anything else you can do.

 

[Chris Knight]

Water borne finishes generally do not take kindly to being thinned. 20% sounds like a huge overthinning IMHO unless the manufacturer allows for this.

 

[ivan]

There's a fair bit of waterbase used in the US and commented on in FW magazine; a RH of no more than 60% is often stated as a requisite - higher and you get extended cure times. The RH outdoors here is usually at least 75% and 95% in damp cloudy weather so not suitable for spraying unless your air make up unit heats the air...Thinning with more than about 5% water may upset the paint chemistry* (unless maker says otherwise)


* Paint is not actually water souluble, but an emulsion of watery and non watery parts (like milk, cream, or salad cream - fats/oils and water mixed) The water is supposed to evaporate and allow a slow (non watery) solvent to meld the non watery bit (the actual finish) into a smooth coat. Extra water can upset the ability of the paint to form a proper coat, or may even to allow slow solvent to evaporate before all water is gone. A lot of tapwater may also affect the paint pH.

 

[cornucopia]

as has already been said 20% is too much especialy in a lower spec paint, i use dulux trade paint everyday and the quality is superb, the most i can thin that by is 15% but 10% is more normal. I think to give yourself a fighting chance try a better quality paint and if your still having issues you can always add some water based paint conditioner which will help improve the spray finish, one of the best conditioners is floetrol

 

[ivan]

My (US based) bro - in law swears by this stuff, didn't know you could get it here. Even if it is about 6x the price he pays.....

 

[cornucopia]

My (US based) bro - in law swears by this stuff, didn't know you could get it here. Even if it is about 6x the price he pays.....

do you mean floetrol or water based gloss?