A PVA Mess!

I could use some advice here please. I have used PVA before. I have always applied it with a small rag and continually worked it into the surface until a nice uniform film stayed put. (or when the beading no longer occurred)
Obviously I could only do this on small molds.
I decided to spray the PVA and what a terrible mess resulted. It was the worst case of fish eye I have ever seen. To save things I got out a rag and wiped the whole mess off.
I started spraying on a very light coat at first and the result looked dry like chalk so I went heavier and heavier until it looked wet. Thats when it went into beads of PVA like chicken pox.
I have seen videos of companies spraying large boat molds with PVA so I knoe it can be done. The trouble is that no one is giving a step by step instruction on how to do it.
Help with instructions would be greatly appreaciated.
Fred

 

Applying pva is childs play !! Dont read what on the lable !!

Ok throw away all that you have read and what you think you know about PVA !!
This is so simple it stupid !!
Ready ??
Always spray pva !!!
brushing !
wiping !
pouring !what ever is a total waste of time and materials!

Take the bowl off your spray gun and pour in 1/2 cup of pva straight from the bottle ! take the same cup and pour in 1/2 cup of cold water straight from the tap !!
Mix together !
Its enough to spray on A 35 foot Yacht hull mould you should have about 1/4 or a little less of the mix still in the gun when you finished !!
I hope you have a good air supply with lots a air !
Wind the air pressure to max 100 psi or more .
On the gun wind the flow controll needle in so its completely shut off so there is nothing coming out when you pull the trigger back !!.
OK!!
Now ready to adjust the gun !!
Hold the gun up to the light so you can make sure there is nothing coming out when you pull the trigger back .
Gradually and slowly wind out the needle till you see a fine even misty spray coming out !!,Usually 1/2 to 3/4 of a turn !
Ok !! thats all you need to come out of the gun!!
Use max air pressure and spray your mould !!
visulise what you are doing quickly and evenly !! stay away from the mould about 600 mm or a little more !
Most important to remember is if you can see the pva on the mould you have to much on !!!
You should not be able to see the pva at all . release the trigger till the spray stops and just air is comng out of the spraygun and blow the air across what you have sprayed !! this will eveaporate the water and dry the pva !when it has completely dried very gently with just the air still coming out of the gun blow dry your hand as well and you will be able to wipe your hand softly across the surface of the mould coated with pva dont stop you hand any where or the moisture from you skin will melt the pva you have just sprayed on .
The finer the spray the better !!
Takes practise and as i say the finer the spray the better it works . If you can see it you have to much !! Remember that !!!!

I have posted this maybe 4 times for people having pva problems and has worked for the every time for them .
When i worked in Australia and i was shown this technique and have taught and show people for the last 20 years ! The place we worked in Queensland we never waxed a single mould all the time i was there we only ever used pva 100% of the time on everything . New Plugs and making moulds . products out of Glass moulds ! even old moulds been laying about the place after a buff and polish !! works really well on boats deck non skid and dosent get dirty wax marks when a deck comes out of the mould . !!
Takes practice !! dont be tempted to doing a heavy spray !!
Spray fine and if you can see you have to much on !!!!
ONCE YOU MASTERED THIS AND SEEN HOW EASY ITS WORKS POST SOME FFED BACK !!FOR OTHERS TO PIC UP ON !!
Just think 50% of what you are putting on is water so when it dries its half of what you think it is !! the thinner the better !!
Its no reall advantage at all trying to spray a second coat !!!. just picks up dust and sticks to the mould , so dont be tempted !!!

 

As Tunnels says, It works, i tried it last year thinking that cant possibly work? but i am a convert!

 

Thank you so mch for your reply !!Still working ok ??
Do you use any wax as well or just PVA ?
Takes a little getting used to the no wax thing but !!
once i gained confidance in the pva as a totall release i was stuck on it but only if i sprayed it myself !

If you have any left in the spray pot just tip iy back in the bottle for next time !!! no waste !! gun is easy to clean out just us water and then clean acetone !!
Thank you keith66 good luck !!

 

Tunnels thank you for sharing your technic. It sounds so out there, from everything I have been able to learn so far, but it makes sense what you are saying. I will definetly try it the way you have described.
There is no arguing with what works. So much in the composite industry seems to be hidden in clouded secrets.
Thanks again.
Fred

 

So much in the composite industry seems to be hidden in clouded secrets !!
Sure is and its only handed on from one worker to the next over time so when staff have been in only one place for a long period of time they are usually way behind the 8 ball and know stuff all !!

I WAS working in Australia , queensland 1986 when i had spraying PVA shown to me and have used it ever since !!
Its almost completely fool proof and so simple !!
I to tried everything ,,even using a fine paint roller once , Just gave up and added more coats of wax .
One industrial place i worked they sprayed pva and then lightly waxed over the top of the pva . was never sure if the pva was still there or not !! .

Something else that works well is Slicone car wax !!Yes silicone car wax !!.
In tahiti wax was really hard to come by so a quick trip to the local garage and came back with car wax !! Just one coat was all they used!!, well rubbed !!!
The the trick was to spray the gelcoat very fine and lots of thin coats so it wouldnt fish eye !,But it worked and we never had one single problem with it !!.even using wet on wet gelcoat spray with multi colour's !!
Every country i worked in i picked up ideas !! some good and some bad ones but everything worked !! I stuck to the good ideas and forgot the bad . Here in China i been here a year and a bit and im still waiting to see any kind of ideas good or bad !! :idea:

 

Thanks as well!

 

So all the mess is no more ??
i hope it workes well for you the 50% seems to give good srap and smooth and cant see anything less its possible to get a spray pattern . !! Thanks and take care !! always here to help !!

 

would a cup gun work? That's all I have. I did get some preval sprayers which are aerosol cans that you screw onto the bottle of whatever you're spraying but they're not for big jobs. I should go ahead and buy a cheap spray gun. This cup gun seem real touchy and its easy to splatter if you don't handle it just right.

 

HI
As long as you are able to mix water and pva together and spray a very fine misty spray any kind of gun will do !! just need to get a flow of air to make sure it dries ! a fan would do after you have finely misted and ever so light coat on you moulds surface if your using mirror tiles you will be able to see the spray and make sure its even all over and fine !!
Please read and understand completely what its all about !! like i said its so simple its stupid !!.Its nothing like what i was shown and did for long time after i first started in the fibreglass industry its nothing like the instructions on the container you buy ! but it works and works well !! Has saved my bacon on more than one occassion thats for sure !!
Some places i worked we never used wax at all just pva !!
Good luck and keep us posted !! so often we never get to hear the end results !! good or bad !

 

Like Tunnels said you really do need a bit more air when you're spraying PVA. I use an inexpensive HVLP cup gun with a 1.4 or 1.8 nozzle for my PVA applications, and it works just fine. Although I've never tried his method I can see the validity in his approach. I just wonder if the spray settings he was taught wasn't more a result of thinning the PVA with water, and then trying to get the reduced PVA to work right. With all that excess moisture in the PVA it's only logical that you'd want a really thin coat and to use your air supply to help dry it in a reasonable amount of time.

Since my little HVLP gun won't put out that much air I use straight PVA (no thinning) and 20 to 25 lbs at the gun. If I shut down the fluid nozzle too far or up the air pressure too much I get stringy little wisps of PVA floating around the shop. I suppose adding water might help but then I'd have to worry about some bug getting stuck in it before it dried...lol.

Mike

 

if you can see it theres to much on the mould !!

Read and understand what was written !! yes its pretty hard to get you head around but it works !! check the comments from others that have been converted and read what they had to say .
IF YOU CAN SEE IT ON THE MOULD YOU HVE TO MUCH ON !!

 

I was getting those white stringy things too using my little preval sprayer. I thought it was cause I didn't have the PVA all the way up over the pipe going into the bottle and air was getting into it. I'm also wondering if when using such a thin coat of release, you have to spray on the resin or gelcoat. I'm thinking if you painted it on it would disturb the layer of release. I think that happened when I tried the Fibrelease. (1153) I guess I didn't let it dry or had too much on.

 

Hi Tunnels,
Oh I'm pretty sure I understand, and I might even try it the next time I'm spaying up a part. I'm not sure I'd be confident enough in my ability to spray up an unwaxed 35 hull with only my memory to serve as a guide when half the time I can't remember where my glasses are. But then again I'm not into bungee jumping, hang gliding, or diving with sharks...hmmm maybe I'm just chicken.

Mike

 

Sunbelt,
I suppose you can induce the little PVA spider webs things in a couple of ways, but it's always been my experience that too little PVA or too much air is the culprit. Of course that's using unthinned PVA which up to this point has been my preferred method. Tunnels obviously has a LOT of experience using the procedure he outlined above, but I'll freely admit that I like being able to see where I've sprayed, or more importantly where I might have missed.

Normally I'd say you're safe to brush, roll, or spray over a coat of PVA, but considering how thin an application you might end up with I'd go with spraying...I was going to say "to be safe" but considering the procedure we're talking about that's an oxymoron.

Mike