Lab Metal CRACKING WHY???

[dennisaikman]

when in doubt follow directions on the back of the can
your statement said you heat cured twice at 200C.
that is 392F
The directions on the back of the can states to heat cure the hi temp lab metal at 450F for one hour. So if you dont do this at 400-450 and you only bake the product at 392F- there is solvent in the repair still and then the solvent comes out through the powder when you bake it and causes cracking
just like paint.
If you apply two coats, you need to heat cure each coat at 400-450F
otherwise you have solvent entrapment.

This is how i did it:

1) Sand blast piece blow off dust and wipe with solvent.
2) Fill with Lab metal and let air dry for 24 hours.
3) Put it in the oven for 1 hour at a little under 200 degrees celcius.
4) Removed from oven and Sanded lab metal and refill with lab metal. And let air dry for 24 hours.
5) Put it in the oven for 1 hour at a little under 200 degrees celcius.
6) Removed to sand it and it has CRACKED

Too expensive $hit for this too happen.

[dennisaikman]

Instructions for Lab-metal and Hi-temp Lab-metal (SO IT WORKS FOR YOU THE FIRST TIME) THESE ARE ON THE BACK OF THE CAN. Customer who posted their failure did not follow directions.

Lab-metal for temps up to 425F for 25-30min. or 350F for constant
Open Can, add a capful of solvent to get to a body filler like putty.
Take out of can with putty knife, spread - if you need to work it, shape it and form it like a body filler, keep putty knife moist/wet while applying.
Allow each coat to dry for 1-6 hours (depends on application) stick your finger nail into the repair- does not leave a mark- sand it and powder coat over it.

Hi-temp Lab-metal - same as above. resistant to 1000F. Must allow air dry for 24 hours and then heat cure at 425-450 for about 30-45 minutes.
if you do not heat cure or bring up to these temps and heat cure at 392F like the posting prior- the solvent will not come out of the repair and it will then come out through the powder in the oven and cause outgassing or cracking.
If two coats are to be applied- you must heat cure each coat.

If all directions are followed (above) This product has been around since 1950 and used successfully by powder coaters because it is one part, metal based and not epoxy based and will accept the charge of powder coating.
Any questions- call Alvin Products www.alvinproducts.com

[Banditperformance]

I did follow the directions, all except I heat cured the regular lab metal. Alowed 2 hrs dry time, at 120F, bubbled like crazy. 3 coats of Lab metal, over 3 days application, 24 hrs between coats, 2 hrs dry @ 120 in oven before coating

[dennisaikman]

you do not need to heat cure the lab metal NOR does it suggest doing that!

[dennisaikman]

Lab metal should be applied no thicker than 3/8 inch at a time.
If Lab-metal is not allowed to dry between coats or you put REGULAR lab metal in the oven to force cure or speed up the cure- you could have mud cracking, outgassing.

[dennisaikman]

Alowed 2 hrs dry time, at 120F, bubbled like crazy-
THIS IS LIKE PAINTING YOUR HOUSE IN THE DIRECT SUN LIGHT

[Banditperformance]

Well, no need to have attitude with me. I was just explaining what I did and what happened. If using a little heat for Lab metal is bad, but necessary on High temp lab metal, maybe there should be a warning on the Lab Metal. "Do not use heat to cure" To help differentiate. I'm sure I am not the first person this has happened too.

PS, I have never painted a house, so I don't know what your talking about.

[JeffL]

I think your troubles are with putting it in the oven. The regular lab metal does say that a heat lamp can be used, but I really don't see the need.A thin coat can be worked within a couple hrs. to knock the heavy stuff off, then leave it overnight to fine sand.

[dennisaikman]

exactly.
Two things happen when paint dries.

First, some of the liquid evaporates. Paint is made up of two parts, liquid and solid. The part of the paint that evaporates is what you smell when you walk into a freshly painted room.

To understand how paint dries, you have to know a little about the difference between liquids and solids.

In liquids, the molecules are weakly attracted to each other. The reason liquids flow is the molecules can slip and slide past each other.

The molecules in solids are strongly attracted to each other, so the molecules cannot slip and slide. As the paint dries, the attractive forces of the remaining molecules increase to form a solid.

making the paint dry too fast- will cause bubbles, outgassing, air pockets

However, in modern paint there is an additional process. As the paint dries, the molecules become so close that the molecules join to form a molecule that is twice the size of the original. The combining of molecules continues until all are connected to form one huge molecule.

[Harleydad]

Originally Posted by dennisaikman

exactly.
Two things happen when paint dries.

First, some of the liquid evaporates. Paint is made up of two parts, liquid and solid. The part of the paint that evaporates is what you smell when you walk into a freshly painted room.

To understand how paint dries, you have to know a little about the difference between liquids and solids.

In liquids, the molecules are weakly attracted to each other. The reason liquids flow is the molecules can slip and slide past each other.

The molecules in solids are strongly attracted to each other, so the molecules cannot slip and slide. As the paint dries, the attractive forces of the remaining molecules increase to form a solid.

making the paint dry too fast- will cause bubbles, outgassing, air pockets

However, in modern paint there is an additional process. As the paint dries, the molecules become so close that the molecules join to form a molecule that is twice the size of the original. The combining of molecules continues until all are connected to form one huge molecule.

I'm still not gonna watch paint dry.