Brushing spray gel coat

Discussion in 'Fiberglass and Composite Boat Building' started by bigjonny9, Oct 29, 2011.

  1. bigjonny9
    Joined: Apr 2010
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    Location: New Zealand

    bigjonny9 Junior Member

    Hi guys I am having a issue with fish eyes in my gel coat. I am not sure whether my gel coat is a brush or spray. when I first touch the mould surface with the gel coat it causes fish eyes all over my brush stroke however if I go straight over the area again it tends to decrease them alot. I wondered if I was not giving the last wax enough time to gas but have followed manufactures instructions. I think the gel coat could be spray could that be the cause? I catalyse at 2%
     
  2. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    It shouldn't fisheye with either type, so something is wrong. It's possible for it to be either the gel coat, mold release or some type of contamination on the mold.

    Is the gel coat old? the viscosity will drop as it ages and this can cause fisheyes.

    Bad batch of gel coat.

    Not the correct type of mold release, or not applied correctly.

    Something on the rags used to wipe off the wax.

    Has anyone used a silicone lubricant anywhere near (in the same building) where you're working.
     
  3. bigjonny9
    Joined: Apr 2010
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    Location: New Zealand

    bigjonny9 Junior Member

    Hi thanx for the reply, Im using Tr standard mould realease wax. The rags I bought from a paint shop Im assuming they are contaminant free. The gel coat is 1 week old as it was a special color I got it made from the manufacturer only last week. I was a little short on application times between waxing but Ive got away with it many times before. Silicon could possibly be viable however It is my home shed and I havent used anything of that nature in there before.Ive never experienced anything close to this before.Bad Batch of Gel Coat? sounds like you could be on to something there.Wax mould release I know there are a couple of different types do you know the differences?
     
  4. latman
    Joined: Mar 2010
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    Location: Australia

    latman Junior Member

    Certain mould releases are too "slippery" in certain uses and they can cause the gelcoats to fisheye (I found that with Frecote years ago). if you use thinner(less viscous) spray gelcoat you would be best advised to lightly "dust " the mould surface first (especially any vertical sections) then hopefuly that will give some "tooth" for the remainder of the gelcoat to adhere to without fisheyes /runs.
     
  5. tunnels

    tunnels Previous Member

    You need to spray a fine coat of PVA release agent over the waxed surface !!Like having a layer of glad wrap between the two !!
    Fish eyes are caused by the gelcoat wanting to pull away from the waxed surface . If the gel coat is thin it does the same thing . Better to spray !! multi fine coats !!
    Leave the wax to gas off 12 hours at least can help !! . Fresh coats of wax are the worst times . The best wax to help with not getting fisheyes is the old Ceara wax ,most of the others fish eye ll the time !!
    If you are hand brushing its an!!!,when you brush put plenty on and last stroke of the brush back goes into its self ! You are not painting you are gel coating it not the same . gel coat you need thickness , painting you want a smooth finish , Not the same dont hold the brush straight up and down lay the brush at about 60 degrees and trail the gel coat back onto what you have already applied and lift off as you brush into the wet coat you have just put on . Experiment !!
     
  6. latman
    Joined: Mar 2010
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    Location: Australia

    latman Junior Member

    I agree Ceara is/was best , I think PLP 1(or 10) is the same , the fisheye problem for gelcoats is sort of similar to prerelease for cured laminates , PVA is hard to apply also over lots of release "films" but it is a sheet of plastic that guarantees no stickup ! (I don't use it personally) The issues I see with brushing gelcoat are numerous , including touching PVA (if used) with the bristles
    ps never use anything silicon based....
     
  7. tunnels

    tunnels Previous Member

    Lots of myths about pva and silicone wax's

    Working in tahiti we always used the standard silicone car wax one coat was all that was required i blinked and turned away i could not believe . It worked always never had a failure ever !! Spraying gel coat was a fine spray with multipal coats one after the other .

    Pva how do you apply ?? wipe it on straight from the botle ? thin it with meths ? Spray it ??

    While i worked in Australia we only used pva never had wax in the factory !!
    Impossible you say ! again time to learn !
    Thin the pva 60%with clean water straight out of the tap put in in a spray gun and spray with max pressure and as fine as possilbe srew the flow need right in and back it out till you can just see it coming out of the gun nozzle . Now spray your mould . Trick is if you can see it on the surface you have to much on !!,Blow lots of air across the surface then it dries almost instantly . Never had any problems never had any dust marks never have any PVA spray marks or patterns any where . Its majic works 100 % of the time on any mould on New plugs making moulds is fantastic . No you dont get any sort of blemishs .IF YOU CAN SEE THE PVA YOU HAVE TOO MUCH ON !!![/SIZE]:eek::D:p:p:)

    If you want to learn about the products you take for granted every day you need to get you head out of that helmet with blinker on and shake your *** out of your comfort zone and work in places that have very little to nothing to work with and open your eyes to the wonders of what other do !! When i set out on my world travels 1985 i thought i knew it all !!,but in less than a month i found i knew nothing hardly worth talking about !!Its now 2011 and im still finding new and differant ways of using things .
     
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  8. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Do you use paper towels or cloth to give the release wax a buff?

    Use some clean cloth, and give the surface a good and serious buffing. Use plenty of cloth. This will very probably already solve 80% of your problem. It is not uncommon for a wax to actively repell gelcoat the first time/pull, but it is annoying indeed.

    About your gelcoat: Please ask the supplier whether it is spray or brush. If spray, then it is more difficult.
     
  9. bigjonny9
    Joined: Apr 2010
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    Location: New Zealand

    bigjonny9 Junior Member

    yes it is spray. I have already pulled two articles off the mould with same result. I will try your suggestion.

    Thanx
     
  10. tunnels

    tunnels Previous Member

    Try a little exsperimentation !!

    If you are having trouble with fish eyes and seethroughs in the gel coat then second coat at a slightly highter catayst ration but add a little of you laminating resin to the gel coat ! Makes it easyer to brush onto the first coat of gel . Also try adding gelcoat to your resin to colour it when you do you first skin of glass ,everything helps to eliminate the look . Adding gelcoat to the resin also adds deepth to the look of things , specially small items . :):D:p:p:p

    Used to use pigmented resin ti finish the inside of some of the smaller boats bing made in one place i worked at . The pigmented resin also had wax mixed in the resin as well so was a really nice way to finish the inside of the hull and the underside of the decks ,and with the small yachts there was no light shine through !.
     
  11. keith66
    Joined: Sep 2007
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    Location: Essex UK

    keith66 Senior Member

    Regarding Tunnels pva spraying technique, i tried it recently, it works brilliantly & i now use it all the time.
     
  12. tunnels

    tunnels Previous Member

    Yes !!! me to !!has saves by bacon quite a few times specially on decks where there is non slip pattern helps to keep the gel coat 100% clean when the deck is demoulded no wax marks any where !! took me 10 years to find that and i had to go to a pacific island and work with a bunch of guys that never spoke any english !!! :D:p:p:)
     
  13. bigjonny9
    Joined: Apr 2010
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    Location: New Zealand

    bigjonny9 Junior Member

    Hey guys I sorted problem!!! Ive since bought a pop corn gun and sprayed it with a awesome result. The problem was that the surface was just TOO SHINY for the brushing technique. As I applied the brush to the surface the tension from the waxed surface caused the gelcoat too repel causing the fish eyes. Let this be a lesson for others haha
    Regards
     

  14. tunnels

    tunnels Previous Member

    Before the days of spraying gel we always hand brushed everything no matter what shape or how big or small it was!. Fish eyes is just brush technique you need to learn to get over them . Long soft bristles in the brush are the other thing you need !. :p
     
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