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Old 04-04-2014, 12:23 PM   #1
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doing my exterior 88 year old cedar siding. Scraping loose paint, alligator and chalking. Half wood is bare and have has old stuck on paint after scraping..What is the best primer for both bare wood areas and old stuck on paint?/ Thanks a lot.

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Old 04-04-2014, 01:21 PM   #2
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If it's cedar, you will need an oil-based wood primer to seal in the tannin bleed that usually occurs with cedar.

Here's an example:
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Old 04-07-2014, 05:33 PM   #3
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This always seems to be a can of worms subject..sort of like religion and politics. i just thought it was a good idea to cover areas that have little islands of old paint still on the house with the Primer RX to lock them before primiing the whole house with oil primer, down but does everyone think that just an oil base prime alone (either cover stain or SW ext. oil primer) will do the same thing as the added step of SW Primer RX?
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Old 04-07-2014, 05:38 PM   #4
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So can some one explain why a slow dry oil primer is better than a fast dry on my old bare cedar? And is this fact? Thanks
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Old 04-07-2014, 06:53 PM   #5
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Quote:
Originally Posted by glenk2007
So can some one explain why a slow dry oil primer is better than a fast dry on my old bare cedar? And is this fact? Thanks

I think the idea is that a slow dry has more time to soak in. Years ago around here, it was common to do a 1st prime of thinned down slow oil, that would almost completely soak in. Then do another prime un thinned.
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Old 04-07-2014, 07:37 PM   #6
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So can some one explain why a slow dry oil primer is better than a fast dry on my old bare cedar? And is this fact? Thanks
When I was a youngster an old man told me " sometimes good things just take a little longer "
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Old 04-07-2014, 09:05 PM   #7
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Water based primers act as "wicks" and "pull" the tannins out of the cedar. Oils do not have that same effect.
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Old 04-08-2014, 07:35 AM   #8
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Thanks everyone so much..I Love Paint!! You all are awesome!!!!
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Old 04-08-2014, 09:21 AM   #9
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Originally Posted by glenk2007 View Post
So can some one explain why a slow dry oil primer is better than a fast dry on my old bare cedar? And is this fact? Thanks
OK…hmm - well, there are a couple of reasons why the system you described is and age old, tried and true, recommendation.

The easy one first - Cedar (especially cedar), is filled with tannic acids. These acids are rich in color and are water soluble - Oil primer, either fast or slow dry, is necessary so as not to pull these acids to the surface (as latex or water-bornes will tend to do), causing reddish, coffee colored stains from bleeding through finish paints…there's 1…

The second and primary reason has more to do with wood in general as opposed to only cedar board. Lightweight boards, like cedar, may pass through an extraordinary amount of water, in the form of vapor, through capillary action - from the interior of your home, through your siding and ultimately through your finish coat(s) of paint (possibly). The problem with this dynamic, irrespective of the affect on finish paint, is the "fatigue" experienced by the wood's fibers by the steady expansion and contractions of board due to this vapor transmissions.

What a "slow drying" oil based primer does in this scenario is penetrates deeply into the board's capillaries, strengthening them and limiting the amount of expansion and, therefore, the amount of moisture they are able to pass (don't worry, if necessary the moisture will find another route of escape - and you'll need to prepare for that). Slow drying oil primers are "long" in linseed oil, which enables penetration moreso than a product that is "long" in solvent. Also, linseed oil hydrates wood which keeps the wood fiber intact…

Personally, I don't like to put a faster dry oil over a slow dry…nor do I like using a faster dry oil for exterior wood application. These primers are seldom recommended as "whole house" primers. Generally speaking, these fast dry alkyds are "short" in linseed oil and are too hard and brittle for responsible use on exterior wood siding. It is almost impossible to stop wood from expanding and contracting, and if any coating within a system is not capable of expansion and contraction it has no choice but to break from the surface in the form of peeling.

In this scenario, if your first coat of slow dry oil primer has penetrated the wood so deeply that it has the appearance of a stain on the surface, a better recommendation would be to either (a) apply a second app of the slow dry oil and allow adequate dry time (often times 48-72 hours) before applying finish…or (2) apply 1 application of an acrylic exterior wood primer because of it's ability to adhere, expand & contract, and "breathe" (pass moisture without film breakage).

I hope this info is more helpful than confusing…Good luck on your project.
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Old 04-08-2014, 03:00 PM   #10
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Thanks Ric, I appreciate your long windedness. I need details like that. So if the first coat of long oil primer looks like a stain rather than solid which will probably happen why would I need to put on a second coat of it or acylic exterior primer. Won't the topcoat cover the stain look? And if so can I use say bullseye 123 as the secong coat of primer?..Thanks again....Glen
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Old 04-15-2014, 08:51 AM   #11
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Ok so now I'm into my exterior house painting project. Oil priming everything. Very tedious and messy....My question is this: Can I prime the old still solid painted areas (a little bit chalky still after tsp) with say a bulls eye123 latex primer and continue oil priming the bare wood areas. Is there something magical about oil priming solid paint areas?
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Old 04-15-2014, 10:07 AM   #12
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Typically you only need to prime the bare wood spots. As long as the old paint is clean and sound, the new paint will stick to it. Nothing sticks to latex like latex.
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Old 04-15-2014, 10:09 AM   #13
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Originally Posted by Jmayspaint View Post
I think the idea is that a slow dry has more time to soak in. Years ago around here, it was common to do a 1st prime of thinned down slow oil, that would almost completely soak in. Then do another prime un thinned.
We did that a lot with deck enamels. We would call it a spit coat. Not sure if that is the correct terms for it or if there even is one.
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Old 04-15-2014, 10:16 AM   #14
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Quote:
Originally Posted by glenk2007
Ok so now I'm into my exterior house painting project. Oil priming everything. Very tedious and messy....My question is this: Can I prime the old still solid painted areas (a little bit chalky still after tsp) with say a bulls eye123 latex primer and continue oil priming the bare wood areas. Is there something magical about oil priming solid paint areas?

If the surface is a little bit chalky still you better take a precaution for adhesion. Don't count on 123 or any regular primer to bond to chalk, even a 'little bit'. It will peel just as quick as anything. Add emulsabond to the first coat, or do a pre treatment like Seal Krete to bind the chalk.

The only problem I see with using different primers is going to be sheen inconsistencies. Different primers provide different levels of... 'Hold out' for sheen. 123 is a hard shiny primer and will maximize sheen of the top coat. A lot of oil primers like Coverstain have a dull, flat finish that reduces the sheen of top coats.
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Old 04-15-2014, 10:55 AM   #15
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well then maybe I should just continue using the SW oil primer on everything (solid left on paint and bare wood). Is oil a little better on slight chalk than latex?

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