Dumb question that i should know the answer to.. shrinkage - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Body - Exterior
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #16 (permalink)  
Old 10-07-2005, 12:36 PM
Member
 
Join Date: Feb 2005
Location: Sheffield, UK
Age: 45
Posts: 61
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Steering things back on course, if I may

I'd totally agree with the trapped solvents explanations, for any of the reasons given.

To illustrate, here's a little story:

We tend to prime all our repairs together, at the end of the day, to save wastage. When I was doing it, we hardly ever suffered shrinkage problems. Now the boss has begun to let our young lad do the priming, we are having regular problems (same product used).

He thinks that if he bombs 3 thick coats of 2k primer on the big repairs, with minimal flash times, he can go home early (and it'll 'hide' his poor filler work). The problem starts the day after. Upon hitting the primer with a DA, you can smell the solvents bursting out! I've even had it so bad, that the primer has popped right through the base and clear during baking!

Besides re-educating him, which is difficult as he is the boss's son, I've found one way around it is to block or DA the primer down early in the day, and leave it to sit as long as possible before final sanding. This seems to give the solvents time to escape, after 'breaking the surface', and shrinkage problems have been reduced.


Clearly, as stated above, the better way would be to take more time applying the primer, and allow plenty of flash time between coats, but maybe my method of 'breaking the surface' could help a little also.

Andy.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 10-07-2005, 12:55 PM
jcclark's Avatar
The Penny Pincher
 

Last journal entry: Hanging Bumpers
Last photo:
Join Date: Dec 2004
Location: Louisville, Ky. U.S.A.
Age: 61
Posts: 1,873
Wiki Edits: 0

Thanks: 4
Thanked 19 Times in 16 Posts
That makes perfect sense to me.
Like Barry pointed out in another thread, that works good for buffing clear
too, after you sand it allow it to sit a few hours and it'll also buff better.
anytime you sand a surface you open it up to dry more.
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 10-07-2005, 01:24 PM
MARTINSR's Avatar
Brian Martin,Freelance adviser
 
Last photo:
Join Date: Jun 2004
Location: San francisco bay area
Age: 55
Posts: 13,118
Wiki Edits: 0

Thanks: 1,293
Thanked 1,138 Times in 1,008 Posts
An example is in my gun set up "Basics":

As an example of the use of a 1.3 tip I did a test once that proved the point well. I shot two panels of metal with a med solids urethane primer. One was shot with a 1.3 super high atomizing top of the line topcoat gun. The other was shot with a 1.5 (or a 1.7 I can’t remember) “hoser” primer gun. Three coats were applied and after a full cure (the one shot with the larger gun took MUCH longer to flash and cure by the way) the film thickness was measured. The one shot with the 1.3 tip was 2 tenths of a MIL thicker! The larger gun laid out the marble sized droplets full of solvent and when the solvent flashed the film shrank.


Now, the 1.3 tip may be too small for some products so check the tech sheet. The facts of the findings won't change.

Brian
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 10-07-2005, 01:29 PM
MARTINSR's Avatar
Brian Martin,Freelance adviser
 
Last photo:
Join Date: Jun 2004
Location: San francisco bay area
Age: 55
Posts: 13,118
Wiki Edits: 0

Thanks: 1,293
Thanked 1,138 Times in 1,008 Posts
Quote:
Originally Posted by jcclark
Well obviously we have a different definition of boast.
I think where the miscommunication is that "boasting" can still be based in fact and not pushing the product.

If the product can safely be recoated in 5 minutes by the manufacturers own testing, then "Boasting" it can do that isn't an issue to me.

I think what you are thinking is that they would "push" the boast to sell product by saying it is faster than it really is. Now, that would be wrong.

Certainly, that happens from time to time. we all over sold ourselves on our first date.

But, really, really, the manufacturer with millions of dollars in products, with hundreds of millions of dollars on the line in warrantees isn't going to push that envelope. They want things to WORK, to NEVER be a problem, that is the goal.

Brian
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 10-07-2005, 08:10 PM
crashtech's Avatar
Technician
 
Last wiki edit: Epoxy primer
Join Date: May 2005
Location: Idaho
Posts: 701
Wiki Edits: 17

Thanks: 0
Thanked 0 Times in 0 Posts
I can't say I have the answer here, but I tend to follow some procedures that help ensure a job will have no visible problems from shrinkage. First of all, never feather filler up onto non-factory paint unless you KNOW it was all catalyzed and well cured. Second, never feather filler up over your paint featheredge unless it has been nicely feathered back with at least 150 grit, preferably 220. Third, make sure the featheredges are in 320 grit before priming. Fourth, let that primer flash off! Don't stand there and look at it, go do something else between coats, and set a timer if you tend to lose track of time. Fifth, don't apply thick coats. Just go one coat extra if needed. Now, I'm sure a guy could follow all these steps and still get shrinkage, but that would be rare, IMHO.

Last edited by crashtech; 10-07-2005 at 08:59 PM.
Reply With Quote Quick reply to this message

Recent Body - Exterior posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Dumb question for ya raidmagic Hotrodding Basics 9 03-14-2005 01:03 PM
dumb question blazinwest Engine 6 12-03-2004 10:10 AM
stupid question but need answer? fireforsin Engine 4 10-04-2004 11:18 PM
Hoodless frame - Probably a dumb question Psionic Body - Exterior 9 01-22-2004 08:01 AM
Hotrodders Guidelines -- READ ME Jon Hotrodders' Lounge 0 06-14-2003 05:08 PM


All times are GMT -6. The time now is 08:32 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.