More blocking

[78-911SC]

I'm trying to fine tune my blocking and I'm not quite sure how precise I need to get. I've done my body work and this is my epoxy primer that I have blocked. As you can see in the picture I still have some dark areas that are very shallow. My question is do I go back and skim coat all of those areas or go ahead and spray my 3 to 4 coats of high build primer, block it and see where I'm at?

[David McLaughlin]

If that's the epoxy coat, I'd skim it with filler then spray the primer. These steps determine how good your final product will be.

[Iciclehead]

Personally I am not a fan of filler, albeit using a high build primer is sort of the same thing, just prefer the high build primer approach (I use Sikkens products)

On the work I have done, I kept on going (spray on a coat of high build/wipe on guide coat/sand) until there were no more low spots that the guide coat could find with a hand long board.

My only concern was film thickness, so I was very careful to sand the vast majority of the high build primer off...took 4 complete rounds and I figure about 250 hours of sanding....

Here is my result, painted entirely in my garage....it can be done....

Dennis

[78-911SC]

Dennis beautiful car. It looks like you did an exceptional job. B/C or single stage? Thanks for your input.

[Iciclehead]

Two stages Sikkens, 3+1 for high build with chromate initial, Autobase for colour, Autoclear for clear.

7 full days of colour sanding once the paint was done....

Dennis

[962porsche]

when your dealing with highs and lows across a panel .
you want your body filler work to be straight as possible . that is the point of using body filler !
this calls for at times the need to skin coat a hole panel .
some may say that's allot of filler but it's not the surface area size that makes for allot of filler but the thickness if the filler that makes for allot of filler .

you stated you used a epoxy primer .
ok that's good but epoxy primers have different uses . some are simply a surface some are medium build and others are high build .

if the primed panel needs a good blocking after your body filler (it should not ) other wise you have missed the hole point of the use of body fillers .
but if it does or you think it may need to be you would use a high build primer .
a guide coat should be used on your last coat of body filler to your last coat of priming .

you should in no case ever want to do more then a double priming of a high build primer .
NEVER !
the reason is if the low is that low you will exceed the limits of what a high build primer can handle . so the mil build of the primer will be to thick and with in 5 years will start to crack ,shrink, peal and delaminate .
if you need to fill low spots that a high build primer can not fill with in 2 applications and you what to use a sprayable product you would use a polyester spray filler .

until you have blocked thru the primer all over the place and still have low spots you have not blocked enough .
once you have blocked and have broken thru all over and still have low spots you would have two options .
they are depending on just how low the low spots are would be skim coat with filler or use a polyester spray filler .

in the case of the photo posted I would opt for skim coating the hole door and QTR with a coat of putty (not a high build body filler ) . then block that with 80 or 100 grit and using a high build primer spray 3 to 4 coats .
again the reason for this is mil thickness of the primers .
even by sanding most of it off you will still be exceeding the limits in the areas were you need to fill .
then there is time and cost of products . to spray all that material to sand it and have it end up on you shops floor is nothing more then a waste .
add in the cost of sand paper and you have pissed away allot of money .
the fact that you have wasted all the time and money to have nothing better then if you just simply skimmed the panel with filler and primed is pointless . in fact you will no dough have a worse substrate by keep on priming and blocking priming and blocking .

products should be used as they are designed to be used .

[78-911SC]

962 thanks for jumping in. I was hoping you would give your expertise. The epoxy primer I used is a surface primer that I sprayed after stripping the entire car to bare metal. I than did some body work and used some body filler. Some of my sanding of the body filler took me back to bare metal in areas so I than sprayed another coat of epoxy primer and blocked. What you see in the picture is that result. If I understand you correctly I take my premium glaze polyester finishing putty and skim the entire door and quarter panel after which I block. I than apply the 3 to 4 coats of high build primer again blocking. Forgive me for my ignorance (this is my first project) do I spray one coat of primer and blocking at a time (only spraying another coat if the blocking is not perfect) or do I spray 3 to 4 coats of primer than block? What grit sandpaper do I use when blocking the high build primer? After everything is perfect is when I spray the sealer on??? Is that the last step before sending it to the paint shop?

[962porsche]

there is never a dumb question or one to need forgiving for asking !

now knowing what you did is better for me to give my suggestion on what to do .
because there are so many lows I would tend to use a 50 / 50 mix of a high build body filler and a putty . there is also a product called half time that is the same thing .
I don't like using half time I would rather just mix it my self .

1st scuff the hole door with 220 or 180 then blow it off good . sand the low spots too as you want the filler to stick.
then skim over the bigger low spots for your 1st application and block them down .
it may take a coat or two to fill the bigger low spots ?
for your last coat you want to skim over the hole door a putty some thing like USC icing .
there is no need to keep spraying the epoxy primer less is better for that so don't worry about bare metal until your ready for a filler primer .

once the door is nice and straight with the body filler you will have bare metal areas .
spot them in with the epoxy primer . there is no need to go over any thing other then bare metal with it .
let the epoxy primer flash off real good then going wet on wet you can spray your filler primer over that .
spray 3 to 4 coats of a filler primer letting it flash good between coats . you do not want to crap any solvents .
once the filler primer drys good for a day or two you have two choices if you feel you need the panel to be straighter you could block the primer with 220 or 180 and prime it again with a filler primer or your other option is to just sand and prep it for top coating .

blocking the hole door by hand is a crap load of work .
I would opt for a air board / long board to knock down the heavy spread areas and then go to a long hand board . they are also called file boards .

also so you do not become overwhelmed with all the blocking just attack one panel at a time .
start with the worse panel that way as you go the work load becomes easier with each panel .