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staining fiberglass doors

cybersportSS | Posted in Construction Techniques on January 20, 2006 07:00am

I am a supervisor for a custom home builder and I am getting different answers from my high end painting subs. For my own house I purchased a Mahogony series thermatru fiberglass door. The company says you must their specially formulated stain to finish the door and not to use any other system. One of my painter says I can use Minwax polyshades or gelstain or even regular wood stain and topcoat with exterior grade poly. Anyone have any experience with finishing these doors??

Thanks

Alex Gluck

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  1. alwaysoverbudget | Jan 20, 2006 07:40am | #1

    i did this a couple weeks ago and did a post and got some good advice,you might search archives and see what you come up with. i used minwax gel and it turned out pretty good.first thing i learned was you brush it on and leave it.i tried wiping like i would normaly stain-doesn't  work.be sure and section off the door doing the panels,then the horizonals then finish with verticals. with the stain laying so heavy it took a couple days to really dry. good luck larry

    hand me the chainsaw, i need to trim the casing just a hair.

    1. atrident | Jan 20, 2006 10:23pm | #2

        Minwax gel works pretty well touching up photo/phony wood cabinets. As you pointed out..dont wipe it off like normal stain

  2. DanH | Jan 20, 2006 10:27pm | #3

    You basically have to use a gel-type stain (actually a transparent paint, the way it works out) on fiberglass. This is because the FG won't absorb regular stain. Not really any reason to use the door mfgr's stain, though, other than to send them more money and a hair of CYA.

    If ignorance is bliss why aren't more people

    happy?

    1. stinger | Jan 21, 2006 01:34am | #5

      Read my post to the OP. 

      What experience do you have with the long-term exposure performance of the stuff you use on fiberglass doors?  Western exposure with no exposure is the worst, especially at high altitudes.

  3. stinger | Jan 21, 2006 01:32am | #4

    I am not there any more, but for the twelve years prior to the company's sale to private investors in 1999, I was ThermaTru's chief  technical guy.  I know all about their stains and clearcoat.

    When I went there in the late 80s, they were selling a finish/stain kit that consisted of a Minwax wood stain and a Minwax exterior polyrurethane product called Helmsman.  It was failing miserably.

    ThermaTru wasn't a stain or paint maker, so it tried everything that was commercially available in stains and clearcoats, to try to come up with a system that would perform.  The first change came about when longterm lab testing showed products by United Gilsonite Laboratories, tradenamed Zar, outperformed all others.

    Out went the finish/stain kits with Minwax, in went the Zar stuff.  But failures persisted, although on a lower level than with Minwax.

    After years of lab development and testing, ThermaTru formulated its own stain and topcoat system, and is still selling it today.  It consists of an oilbased stain with additives that lend it better adhesion to the SMC skin (read: fiberglass) than other stains, and a waterborne topcoat that outperforms everything else by a factor of three to five.

    Your painting subs are only looking at application, not performance.  You can use gelstains and polyurethanes that will "work," i.e., the doors will look good for a sale and closing, but the finishes won't perform like the ThermaTru package. 

    Beware these guys.  They want the easy route of using stuff they can get from their regular suppliers, and they don't want to use a tricky waterborne clearcoat that has a learning curve.

    1. cybersportSS | Jan 22, 2006 08:05am | #7

      thanks for the great info from an insider. When you say it has "a learning curve" is this a stain sytem I can apply myself with success or do I have to find an expert in applying these finishes. My painting subs say "i'll give you one of my guys for a day, no problem", but I am wary of these workers who never even follow manufacturers instructions.

      Is there a product I can use to practice my mistakes on?

      Thanks

      Alex Gluck

      1. stinger | Jan 22, 2006 03:50pm | #8

        Alex, the ThermaTru stain kit comes with a good china bristle brush, which is the tool you'll need, along with a big clean rag, to do the staining.

        The rag is torn in half.  One part will be used to apply the stain, the other part is used to clean the stain from the brush.

        Starting with the panels and their molding surrounds, stain is applied liberally with the rag.  Wipe a lot on so there is complete coverage, then wipe to remove some of it where it's globbed.  The result should be a nice complete cover.  Don't worry about rag marks or swirls.  The brush hasn't been used yet.  It's the secret.

        Stand back and wait a bit, maybe five minutes, for the stain cover to flash away some of its solvent.

        The brush is now used dry, and you have the clean half of the rag in your other hand for frequent cleaning of the bristles.  The brush is used to "move" stain where it is needed for cover, to remove excess stain, and to achieve a uniform film brushed in the direction of the wood graining molded into the surface.

        It is vigorous work, and you may break a sweat.  The rag is used very frequently to clean the stain from the brush bristles as you work.

        Panels are completed first, stain, flash, brush, then all the flat stiles and rails are done.

        The brush is essentially the "stain removal and distribution" tool, and can be used to achieve a thicker or thinner film (read: darker or lighter color) on the door.

        The stain must fully cure before the topcoat goes on.  Read the directions.  A warm-season overnight is recommended.

        One feature of a stain job on a fiberglass door is that if you don't like the stain results (and this is before the clearcoat goes on . . . very important), mineral spirits and a clean rag will take the stain all off, and you can start over.

        The topcoat goes on in three or four thin coats, working quickly.  It's a waterborne, and cures quickly.  You might get three coats on all in the same day.

  4. omaha | Jan 21, 2006 06:45am | #6

    As a pro painter I would caution you strongly against using Minwax polyshades.  The problem is adhesion.  We have had several jobs where the home-owner wanted to "touch-up"  their woodwork and thought using a stain and poly in one can was a good idea.  Not such a good idea when we taped on it.  It will peel off and leave major finish damage.  Touching up after a peel is almost impossible.  The tape we used was a medium tack.     I would use the staining system the door company recommends.  Most gel stains are very hard to use.  Staining a fiberglass door is an art and a very time-consuming one at that.  Good luck.  

    Brian

  5. epicjohn | Aug 08, 2020 07:52am | #9

    Hi guys, this is my first hand experience with fiberglass painting and staining;

    I work for Epic Doors which manufactures high-performance fiberglass entry doors. We evaluated several paint suppliers including TruCoat 623, Sherwin Williams Polane 2K Acrylic, and Aquasurtech D200.

    We were looking for an environmentally friendly, single component water based paint that was super durable, had great adhesion and laid down smooth.

    Based upon our evaluation we selected TruCoat 623. It was much more environmentally friendly than Polane 2K and is a single component and https://TruCoat.Us had better adhesion than D200 and was priced better.

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