Pinholes in gelcoat after spray

[searaytuna]

I just sprayed gelcoat last week and had a good shine after buffing with polishing compound. I noticed today that there are these pinholes everywhere in the gelcoat. What might have been the cause of this? Thanks in advance.

[ondarvr]

Porosity can be caused by many different things, but spray technique is the most common reason, apply too much too fast or too thick and pin holes or porosity can be the result. With more information I might be able to give you better idea.
Type of spray equipment, air pressure, tip size, catalyst %, type of catalyst, color of gel coat, air temp, mold temp, thickness (mils) of gel coat, age of gel coat. Was this a repair or gel coat in the mold?

[searaytuna]

Originally Posted by ondarvr

Porosity can be caused by many different things, but spray technique is the most common reason, apply too much too fast or too thick and pin holes or porosity can be the result. With more information I might be able to give you better idea.
Type of spray equipment, air pressure, tip size, catalyst %, type of catalyst, color of gel coat, air temp, mold temp, thickness (mils) of gel coat, age of gel coat. Was this a repair or gel coat in the mold?

I think you're probably right about too much too fast (in my hind thought). THis was a project where we took the boat out few miles to spray. It was a fairly warm day-mid 70's, a bit misty in the early in the morning. I was using a 2 mm tip, gelcoat color is white and it was dated for less than 2 months. At or a bit less than 2%, and this was a repair. On the final coat I used wax/surfacing solution.

I am thinking mist coupled with too fast application of gelcoat. Damm. I reallyt wanted to do a good job on this boat. THe polished gelcoat doesn't look too bad if you can overlook all the pores.

[ondarvr]

When using wax solution in cool (mid 70s are good) weather you need to be careful, at times wax may start to solidify as it rapidly cools when leaving the spray tip, this is even more common when acetone is used to thin the gel coat. These small wax chunks can cause pin holes and/or porosity.

But like you said it just might be too much too fast.

[fiberglass jack]

sounds like the gelcoat gased on u and the gas was traped in the gel looked good till you sanded whiched open them up on u **** happens , if you decide to spray it again heres some tips spraying gel on a repair it totally different to spraying in a mould ,u have to change the gel coat from prodution to repair u must thin it down by a few ways 1 acetone 2 styrine 3 duratec with the first 2 u will have to add air dry wax or spray a coat of pva over the repair after applying the gel i normally use acetone as the styrine will yellow in time ,first add the wax about 2% then add the hardner about 2 again mix really well then add acetone say 2 parts gel to 1 part acetone some times a little more depending on the gun i have used .7 in the past .spray the gel coat one pass at a time and let the acetone to flash off dont worry the gel in the gun will take a good time to kick as it is retarded with acetone . slowly build up the area make sure you dont have high presure as this will cause orange peel and is a bitch to sand when you have the area painted and r happy thats there is enough material clean out your gun and fill it with some acetone and a little airdry wax and very lightly spray over the area u have just sprayed you will see it flatten before your eyes and save a couple of hours of sanding ,one thing make sure you had the wax at the begining so that the gelcoat is chemically balance this should help stop those pin holes

[eyes]

Hey fiberglass jack, do you know a product called waxol?
I've been told that it can be mixed in the gelcoat for finishing.

[fiberglass jack]

i have heard of it its a paraffin wax which is use in airdry wax it sould work i have even gratted candle wax and let it dilute in styrine and used it for wax

[eyes]

I haven't use it yet but will on a project i'm working on right now (Flare boat). I have a friend who is also a supplier (resin, mat, gelcoat...) here in D.R. that will guide me for this matter. I will post the gelcoat-waxol mix ratio later on.

[bluethunder12]

never used the waxol 19 years never heard of it learn something new i suggest using patch aid witch is added to your gelcoat it gives you a tack free finish and your ready to sand i usually use a 320 da and 1000 wet then agood buffing compound aqua buff, all this stuff if you have access to a local boat company or a supplier i go to our local boat manufacture anyways sorry for the priosity it's a pisser and there is really no way of getting reed of it x-cept to repaint goodluck

[eyes]

Waxol is used mixed in the gelcoat to spray the final coat. It's paraffin diluted in styrene. Once it start to cure it comes out sealing and helping cure the gelcoat protecting it from the air (Its not a catalyst and is mixed before adding the gelcoat catalyst). Once cured, the gelcoat can be brought to a high gloss using the normal procedure, finishing with wax.

[searaytuna]

Originally Posted by fiberglass jack

sounds like the gelcoat gased on u and the gas was traped in the gel looked good till you sanded whiched open them up on u **** happens , if you decide to spray it again heres some tips spraying gel on a repair it totally different to spraying in a mould ,u have to change the gel coat from prodution to repair u must thin it down by a few ways 1 acetone 2 styrine 3 duratec with the first 2 u will have to add air dry wax or spray a coat of pva over the repair after applying the gel i normally use acetone as the styrine will yellow in time ,first add the wax about 2% then add the hardner about 2 again mix really well then add acetone say 2 parts gel to 1 part acetone some times a little more depending on the gun i have used .7 in the past .spray the gel coat one pass at a time and let the acetone to flash off dont worry the gel in the gun will take a good time to kick as it is retarded with acetone . slowly build up the area make sure you dont have high presure as this will cause orange peel and is a bitch to sand when you have the area painted and r happy thats there is enough material clean out your gun and fill it with some acetone and a little airdry wax and very lightly spray over the area u have just sprayed you will see it flatten before your eyes and save a couple of hours of sanding ,one thing make sure you had the wax at the begining so that the gelcoat is chemically balance this should help stop those pin holes

So you spray acetone with waxing/surfacing solution? Doesn't this weaken the gelcoat at all? I just sprayed a boat today, and just used pva after the final coat. Thanks for your tips, I'll try that.

[ondarvr]

Acetone can cause problems when mixed at 50% and isn't recommended to be used to reduce gel coat at all. People do use it though, and in small amounts (<10%) it normally doesn't do any harm. It's better to use patchaid type products that are formulated for use in gel coat, you'll get a much better repair and be able to do it faster, plus most have the wax in them already. Using PVA will work just fine too.

[searaytuna]

I use duratech 759(I think) thinner. I've read somewhere that duratech contains surfacing solution & thus no pva required?

[OSM]

Am I to understand that for repairs you recomend gelcoat with wax?

We use two versions of the same gel coat, one without wax which is applied to the mold and brushable gelcoat with wax for interior surfaces such as bilge etc.

[fiberglass jack]

thats right with out wax the gelcoat will stay tacky gelcoat needs to be blocked frow the air to dry hard thus the reason for the wax a coat of pva will also work even some waxed paper over the repaip will do the trick