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Author
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Topic: Restoring unflown Apollo Avcoat ablator
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SpaceAholic
Member Posts: 4437
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 04-20-2009 10:39 PM
   
There are a number of specimens of unflown Avcoat 5026-39HCG circulating in the community that have originated from a single source, a now deceased AVCO engineer who retained a small hord of 12x12 inch test blocks. Over the last several years, these have been making their way into collectors hands courtesy of eBay, primarily as sectioned smaller pieces of the original larger blocks. Native AVCOAT exhibits high surface porosity and doesnt take a polish very well. The specimens offered for sale unfortunately had a laminate or varnish applied to them post production (not by AVCO) to enhance their appearance. Being a purist I prefer to exhibit them in their original form. The pictures show a smaller AVCOAT sample in the collection targeted for restoration prior to sanding (with its laminated glossy sheen) and then the subsequent result (dull, lighter patena) compared to an un-resurfaced artifact.The actual process is very simple, starting with application of 80 grit and then moving from 180 to 220 fine grit sand paper. Estimate no greater then 1/16 inch material was removed per surface. Lacquer/varnish removers are not recommended because of possible chemical interaction with the base material. Avcoat is readily responsive to sanding (a similar process is used for finishing the actual Apollo TPS surfaces). NIOSH M95 Mask strongly recommended with lots of dust being liberated. (Avcoat particulate hazards are unknown, why take the chance). After completion of sanding, I used a dye free paper towel with distilled water to gently clean off any residual dust from the artifact. A caution: this technique will remove the ORIGINAL AVCO applied manufacturing/inspection stamps - in cases where the original stamps exist on your block, consider limiting restoration to the sides not bearing these stamps - offering the viewer a look at the "natural" appearance of AVCOAT while retaining intact the original stamps. In some instances there are stamps applied which are NOT ORIGINAL to the artifact (an example can be seen in the photo of the restored piece - this stamp was supplied by the original owner to enhance the AVCOAT after cutting and just prior to application of the lacquer. Because they are not original, I have no compunction about removing those). Contrast with the larger block in the images below - which does possess original AVCO inspection and manufacturing markings. Click on images for higher res photos:  
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Scott Schneeweis
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