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Old 03-19-2006, 07:39 PM   #1
mike@af
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Scratchbuild Seminar 4-Putty

Scratchbuild Seminar 4-Putty

This seminar will be very in depth as it often causes the most trouble. People often have difficulty knowing which putty is the best for them and their application. Many time people choose the wrong putty due to lack of knowledge about them, so hopefully this will help you pick your putty.
I have divided it up into chapters, denoted by the large red text, and sections of each chapter denoted by the italic blue text.

Types of Putties

General Putty Information
Putties can be very useful, but they can also turn on you when after you paint. There are several varieties of putties, each have their pros and cons and each have their special uses. One part putties while they are the easiest to use for a lot of people, they can really make you cry after you paint. One part putties dry by evaporation of moisture. This will cause shrinking, and the shrinking continues on over a long period of time. After painting the putty continues to shrink, and can ruin a perfect paint job. One part putties should be used for fixing very small pinholes and scratches. Bondo's Spot/Glazing Putty is intended for just that, fixing little tiny spots, and glazing scratches. Many people have thought that the Spot/Glazing Putty can be used for modifications, and filling. Unforuntately people are blinded by how easy it is to use and cant see the aftermath. Don't try using one part putties where a two part putty should be used just because you don't want to mix. If you do, you will end up spending more time in the long run trying to remove the putty and fix your mistake. Caution: Stay far away from one part oil base putties. When they are wetsanded they fall apart, plus they are incompatible with many types of paints.

Two part putties should be used for filling, major body mods, and other stuff. There are several types of two part putties; Bondo Body Filler, Evercoat Everglaze, epoxy putties, and polyester putties to name a few. Two part putties are much better than one part putties. Two part putties require the base, and the catalyst. By having two parts the putty cures chemically instead of physically. Since it cures chemically it cures much faster, creates a much stronger bond, doesn't shrink, and doesn't absorb paint. Since two part putties are much stronger they can be used for filling without any problems. Two part putties are reccomended as much as possible. If you have a couple scratches and pin holes, wait until you mix another batch of two part putty and fill the holes and scratches that way. You will have a much better result with two part putties. Another benefit is they don't absorb moisture when wetsanding (some one-part putties do).

Body Fillers
Body fillers are excellent two part putties. They cure quickly, dry hard, cure chemically, and best of all they sand easily. Body filler's main benefit is that they sand very well. When they cure they are hard enough to withstand working conditions, yet soft enough to cut with a razor blade or hobby knife. Sanding is extremely easy with body fillers. When cured it can be molded into the desired shape with some 100grit sandpaper, and then smoothed out with some 400-800grit sandpaper. Side Notes: Bondo Body Filler does not stick to plastics. Evercoat Euroglaze is an excellent two part glazing putty that does stick to plastic. Evercoat products are higher end putties but they are much finer and sand smoother than Bondo products.

Epoxy Putties
Epoxy putties are superb for attaching pieces where asthetics are valued. Epoxy putties are super adhesive and super strong for attaching pieces back together. They can also be sanded into a desired shape. So if you need to put something back together, but the joint needs to look good, use epoxy putty instead of epoxy. There are several grades of epoxy putties. Marine and automotive epoxy putties, and model epoxy putties. There are several flavors of model epoxy putties that come in a variety of grit. The grit is determined by how smooth, and how fine the particles are. Marine and automotive putties are almost as good as model putties and comparitively are more efficient because of the cost. Model brand epoxy putties are normally more expensive and harder to find. Marine and automotive putties are less expensive and easy to find and do the job just as adequately. The downside to epoxy putties strength is the ability to be sanded. Epoxy putties are extremely hard to sand since they are very tough, and they also produce a very fine dust and easily clog up sand paper. Also once its on there and cured, its not coming off easily. However, even though they are harder to sand, they can be formed into the desired shape before they cure. The reccomended use is for creating asthetically pleasing joints, not filling and shaping. Epoxy putties also stand up to many varieties of solvents.

Polyester Putties
Polyester putties are two part putties that are a similar cross between a body filler and a glazing putty. Polyester putties can be sanded very smooth and are very good for filling, and shaping. They sand very easily, but are very durable. Just like body fillers, they can withstand many varieties of paints, but not solvents. The glazing factor is they polyester putties can be spread very thin and then sanded smooth for a nice glaze coat. If you need to fill tiny pin holes or scratches polyester putty is reccomended because it will not shrink like a one part glazing putty.

Glazing Putties
Despite the easy use, these putties can come back to haunt you. Many people think they these putties can be used for filling, shaping, and "building". That is a very misleading interpretation. Glazing putties use is all in the name, glazing. Don't try to use it to fabricate. One part putties shrink; the more you use, the more it shrinks. Glazing putties are decent for smoothing plastic joints, or mould lines. Once again, do not use one-part glazing putties for building; the results will be disastrous after painting. When painting a really good sealer should be used because one part putties absorb the moisture and reducers out of paints. To be safe, and to save time, don't use one part putties. One part putties lead to disaster 75-80% of the time.

Super Putty
There isnt a real name for it, so we will call it super putty. Super putty is a good way to make super strong CA joints. All that sanding dust that you make from plastics and putties isnt a waste. When you use CA for a joint sprinkle some of the sanding dust on the CA while its wet and it will create a super strong joint that is shapable. Its best use is for attaching styrene together. Its almost like a superglue filler. Its very handy, but not an alternative to a filler or epoxy putty.

Putty Warnings
This is the most important part to using putties, its about your health. ALWAYS wear a respirator, even when sanding. The vapors (when mixing) and particles (when sanding) can get in your lungs and affect your brain cells. A dual cartridge resperator is reccomended, if you do not own one you should invest in one. They only cost about $30 and can be purchased at many home improvement stores. The paper particle masks are only efficient when sanding. Be sure to mix the putties in a very ventilated area. Now don't let these warnings scare you from doing body mods, or using putties, just play it safe. The warnings on the putty labels warrant death, and other illnesses. Those warnings are a little drastic, but always keep your health and safety in mind.

How to Use Putties

Choosing the Correct Type of Putty
Think about the benefits and drawbacks of each type of putty, and then compare it your application. If you want to fill some holes, or build a body kit use a body filler or polyester putty. If you need to put to car halves together, use an epoxy putty because it creates a strong joint and can be aesthetically pleasing. If you fixing seams, use a polyester or two part glazing putty. Yet again, stay away from one part putties. Many people swear by Bondo's Spot/Glazing Putty but the long lasting results are displeasing and will cause a lot of agony.

General Application Information and Preperation
Remove the paint, dust, grit, and grease. Putties adhere better to a rough surface instead of smooth surface. Rough up a metal surface using some 100-150grit sandpaper, rough up plastic surfaces with a 220 grit wet/dry sandpaper. If you are applying a putty over aluminum, steel, stainless steel, or other type of non-white metal you must spray a sealer or epoxy sealer/primer over the metal first. The resin in the putties can react with the metal and corrode the metal and make for a bad putty job. Primers are not sealers (putties can eat through primers too), be sure to use a good sealer or epoxy sealer/primer.

Application
Read the label for instructions on how to use the putty. Each putty has a certain mixing ratio. Bondo Body Filler is usually mixed to a nice pinkish khaki color. Evercoat Euroglaze is usually mixed to a nice light blue color. Epoxy putties usually are a one to one mix ratio of base to catalyst. Read the instructions on how to mix. After awhile you will become accustomed to the mixing ration and will be able to mix by eye. Go to the dollar store and pick up a large pack of popsicle sticks to mix polyester, glazing, and body fillers. Don't forget to wear your respirator.

Shaping/sanding
Use a variety of automotive wet dry sand papers. Automotive sandpapers are the most accurate grade of sand paper. 3M automotive wet/dry sandpaper is excellent quality and can be picked up at most home improvement and automotive stores. Most automotive wet/dry sandpapers start at 220 grit, for that reason it is ok to use standard 100 grit sandpaper for the initial shaping of putty. Use a variety of sandpaper from 100 grit all the way up to 1500-2000grit.

Needle files are also superb tools to shape putties. Make sure you have a rag near by and consistently wipe the file on the rag every few minutes to keep it from clogging. Files load up very easily but are still excellent tools. To unload them either use a file card or soak them in lacquer thinner or another solvent.

Dremels can be used for the rough sanding. When you the roughed out shape with a dremel use sandpapers and needle files to do the intermediate and final sanding and shaping. Only use the dremel if you feel comfortable in using it.

Don't forget to wear your respirator.

Paint Prep
Standard procedures apply usually. The only difference is that a good sealer should be used before spraying the primer. Some putties will aborb the primer and reducers and be cause for a variety of problems. If you don't want to spend the money on an epoxy sealer, there is a home improvement sealer called Zinser BIN. Zinser BIN seems to be a pretty good sealer so far, and is compatible with most primers. Zinser BIN can be found at Lowes and Home Depot for about $5 for a spray can.
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Old 03-19-2006, 08:33 PM   #2
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Re: Scratchbuild Seminar 4-Putty

Great article as always. Added to ScaleWiki
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Old 03-19-2006, 09:53 PM   #3
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Re: Scratchbuild Seminar 4-Putty

thx Mike, now i feel a little more confident using putty.
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Old 03-19-2006, 11:27 PM   #4
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Re: Scratchbuild Seminar 4-Putty

Thank you professor! I've done all right on my own so far, but now it looks like I can expand a little bit! I plan on getting a few extra putties and a bunch of tools within the next 2 months.

Thanks for putting in the time to do this!
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